Framing Sustainability: Optimization through Technology Implementation and Behavior Change

I took a long break from this blog, and since my last post I've been busy helping companies along their own path toward a more sustainable existence. It's pretty interesting and enjoyable work. Lately I've been reflecting on some of my experiences.

I like to think of our society’s path toward sustainability as a huge and complex optimization problem. The goal is to maximize the goods and services provided to society while staying within indefinitely sustainable limits of natural capital depletion, environmental impact, and human health impacts. However, it is difficult to quantify the sustainable limits of our varied ecosystems (e.g. how much CO2, mercury, and other emissions can be safely absorbed on a continuous basis?). So alternatively, the goal can be stated as the ability to provide all people with the basics of healthy food, clean water, shelter, and sanitation while producing as little environmental impact and human health impacts as possible, minimizing natural capital depletion and investment cost, and does not sacrifice the ability of future generations to provide the same necessities.

Taking this a bit further, our collective journey to sustainability can be framed as two interwoven and equally important (like a yin-yang relationship) approaches – implementing technology and changing behavior. Both of these approaches will be required to get to a sustainable future. I have no concerns about the technology side of things, I am confident that humanity's technological prowess will continue to expand and astound, and personally think a large portion of short and medium-term sustainability goals can be realized with existing technology. Overcoming resistance to change is, I feel, the biggest obstacle to transitioning to a more sustainable society. I follow a lot of news feeds, blogs, research, and other sources of information on a daily basis to stay up to date on the state of the world of sustainability. Typical hot topics in sustainability usually include renewable energy, green building, transportation, energy & water efficiency/conservation, greener products and manufacturing, performance benchmarking & tracking, strategic planning, transparency/disclosure, green marketing, organizational purchasing policies, recycling & composting solutions, food & agriculture solutions, regulatory drivers (policies & incentives), green certifications, and probably a lot more that aren't off the top of my head right now. So really, most of the collective topics on sustainability are related to technology – innovation, policy, marketing, etc. At first glance, that makes sense to most people. If we're going to get on a path to sustainability while maintaining our current habits and standard of living as much as possible, we'll have to implement a lot of technology. Our society tends to lean toward technology as the answer that will enable our sustainability. Technology is already and will inevitably be a huge part of our future. But technology also allows us to maintain our habits and lifestyle with minimal change in behavior, and it alone is likely not enough in the long term. Even in the short-term it’s often not as efficient or effective as a change in behavior. I think we can supercharge our results and merge onto the sustainability highway sooner by changing only a little. An example of a great combination of technology and behavior change is energy usage reduction based on peer comparisons achieved by upstarts Opower and Efficiency 2.0.

Reflecting more on my personal experiences, I've observed interesting disparities among client organizations. For example, some companies execute the plans and recommendations that my team provides and realize the value proposition that we've outlined. It's a great feeling when that happens. But some other clients are excited to hear about the plans and recommendations, but then do nothing (or something so minimal no real results are achieved). The latter usually occurs because the company lacks a champion with the authority to enable change from within. This is frustrating since I know each of our clients will benefit from the recommendations. Why don't they want to take back their used product which can easily be recycled and decrease material costs? Why don't they install the recommended low flow shower-heads or occupancy sensors? Why don't they want to install that new scrap drying system that will reduce waste and payback the investment in only a few months? It's easy for me to see the value and benefit of implementing these solutions, but I understand that there are conflicting incentives in business. Most often there is a focus on short-term results accompanied by a cultural resistance to change.

Better managing change will accelerate our current progress toward sustainability. Greener habits and technologies adopted at work and school can easily spread to family, friends, and colleagues in other organizations. I think sustainability professionals in general need more discussion of change management methods and better integrate them into sustainability strategies and recommendations. Not to diminish what's already being done - there are some really good publications, methods, and tools that address organizational and social change in a sustainability context. But not a lot (based on the anecdotal data point of what I read every day). We can and should do more, and now that I've stepped back to look at the bigger picture, I am going to keep this in mind when I am dealing with those clients that are more resistant to change than others.

How do you overcome resistance to change? If you have thoughts, experiences, or strategies on how to engage communities or organizations on implementing sustainable practices or technologies, please share! Everyone can benefit, learn from, and leverage your wisdom.

Book Review: The Ecology of Commerce

Book Title: The Ecology of Commerce: A Declaration of Sustainability (Revised Edition)

Author: Paul Hawken

ISBN: 978-0061252792

Last week I received a recommendation to read this book, originally published in 1993. Eighteen years later, this book contains a timeless message that is even more urgent in today's world. I finished the 2010 revised edition yesterday, and I highly recommend it.

The Ecology of Commerce is both a condemnation of our society's unsustainable trajectory and a call for the business and industrial world to lead us toward a truly sustainable path.  As the author states, "If this book has one purpose, it is to imagine and describe how businesses can act in ways that are restorative to society and the environment."

Through his "Take, Make, Waste" classification of industry functions, Hawken clearly explains how the industrial revolution started us on a path of rapid exploitation of finite resources and the world's inability to absorb all the toxins that we are dumping into the environment. With regards to the fundamental decline in biological development that we've failed to comprehend, Hawken states "recycling aluminum cans in the cafeteria and ceremonial tree plantings are as effective as bailing out the Titanic with teacups."  In the telling of the true story of the reindeer on St. Matthew Island, Hawken provides a wonderful metaphor of the potential tragic effects of an unsustainable path.

These are messages many of us have heard before and are eloquently communicated in this book. The apparent incompatibility of business and ecological goals are acknowledged by the author - "Business believes that if it does not continue to grow, it will harm itself. Ecologists believe that if business continues its unabated expansion, it will destroy the world around it." But Hawken rejects that notion of incompatibility and puts forth an intriguing argument for a path to sustainability with business leading the way toward a "restorative economy" where production and distribution processes are transformed to mimic cyclical systems found in nature. He summarizes this concept well - "Rather than argue about where to put our wastes, who will pay for it, and how long it will be before toxins leak into the groundwater, we should be trying to design systems that are elegantly imitative of ecosystems found in nature. Companies must re-envision and reimagine themselves as cyclical corporations whose products either literally disappear into harmless components or are so specific and targeted to a specific function that there is no spillover effect, no waste, no random molecules dancing in the cells of wildlife. In short, no forms of life must be adversely affected."

The author outlines a three-part approach to becoming more sustainable: 1) Eliminate waste (entirely) from industrial production, 2) Change from an economy based on carbon fuels to one based on current sunshine (e.g. photovoltaics, solar thermal, wind, waves), and 3) Create a system of accountability and response that support and strengthen restorative behavior.

On the policy front, Hawken argues that our current "market system" is somewhat backwards in that it can reward the businesses who have the greatest externalities in its business model. He outlines some policies that we might enact to account for some of these externalities and reflect a more accurate market economy. For example, the government could enact a carbon tax that is equally offset by the repeal of payroll taxes. That makes it cheaper for companies to hire employees, puts more money in employees pockets, and provides a clear incentive for companies to lower their tax bill by reducing their use of carbon-based fuels. This is something that both sides of the political spectrum could embrace because it helps the environment without a net increase in taxes, promotes job-creation, and could actually lower taxes over time as companies switch to renewable fuels.  Other examples are equally compelling, such as fertilizer & pesticide taxes offset by reduced income taxes and farm subsidies; a gas tax as a form of "pay-at-the-pump" auto insurance; wildlife and traffic congestion utilities; UN weapons tax; and others.

In summary, the Ecology of Commerce is a great read for both novices and subject matter experts of industrial ecology. It is well written, well organized, and contains great ideas for which industry leaders and policy makers can embrace and take action. 

Book Review: The Vertical Farm

Book Title: The Vertical Farm

Author: Dr. Dickson Despommier

ISBN: 978-0312611392

The Vertical Farm is an impassioned plea for nothing less than the fundamental transformation of the way humans grow food. The purpose of the book is to make the case that current agricultural practices are completely unsustainable and that the vertical farm is a simple and technology-ready solution that can remedy this problem, with the ultimate potential of allowing waste-free cities with plentiful food and clean water supplies. I originally learned of the concept of an urban vertical farm from conversations with a colleague. It seemed an interesting topic and concept so I bought this book with the intention of learning more details. 

The book starts with an overview of the history of human agricultural, even detailing the origins of some of the major staple crops in various regions of the world thousands of years ago. This was a bit too much in my opinion, but is an informative review nonetheless. As the author transitions into describing modern agricultural practices, he gradually makes his case for the unsustainable nature of it all through some reinforcing facts, such as:

- 70% of the freshwater used on earth goes to irrigation

- In the US, 20% of fossil fuels are used for agriculture 

- The US imports more than 80% of its seafood, mostly because our river estuaries (traditional havens for sea life) have been severely damaged by agricultural runoff

- To feed the projected increase in population in 2050, an additional land area the size of Brazil will be needed to grow food using traditional farming methods (key point: this much additional arable land doesn't exist) 

- According to a 2005 study, the increasing levels of groundwater salts in the central valley of California (where a significant portion of US food is grown) will cause the agricultural failure of the area within 25-50 years unless another method of supplying fresh water can be found (this is separate from the fact that the dwindling supplies of water from Northern California may cause water shortages as soon as 20 years from now); the projected obsolescence of the California agricultural sector has also gained public concern from Energy Secretary and Nobel Prize winner Steven Chu

- The citizens of New York City could generate about 900 GWh of electricity per year simply by incinerating human fecal waste instead of traditionally treating it and discarding 1 billion gallons of grey water into the Hudson River every day

Though the overall argument is persuasive and I agree with the conclusion of the author, the argument as written was not always as focused as it could have been, hopping back and forth between topics and points across chapters. A lot of the concepts are arguably well-known enough to not need so much explanation. I felt this part of the book could have been condensed and better organized.

Finally (and almost half-way through the book), the author begins to talk about the vertical farm concept. Not intending to diminish its value, the concept is basically a very sophisticated and large-scale version of hydroponics and/or aeroponics integrated with other urban systems. The author outlines 11 basic advantages of the vertical farm over traditional farming (quoting):

1. Year-round crop production
2. No weather-related crop failures
3. No agricultural runoff
4. Allowance for ecosystem restoration
5. No use of pesticides, herbicides, or fertilizers
6. Use of 70-95 percent less water
7. Greatly reduced food miles
8. More control of food safety and security
9. New employment opportunities
10. Purification of grey water to drinking water
11. Animal feed from post-harvest plant material

Some very good color photos and concept sketches are included to help the reader visualize what the author is describing. However, coming in at 320 pages and written by a respected microbiologist, I expected a bit more detail regarding the systems and processes within the vertical farm building and potential integration points (of course, at the same time I did not expect a text book and am aware this was written for the average layperson).

The vertical farm is a great idea based on existing technology. I enjoyed reading about it and sincerely hope that it gets some traction from angel investors or government policy support. It has the short-term potential to locally feed the world's growing population centers, and the long-term potential to transform the world's food supply into a sustainable reality with plenty of environmental benefits. If you haven't heard about vertical farming and want to learn more, I recommend this book. Even if you are already aware of the concept, this book will reinforce some of the ideas and you may learn a few new things. Quasi-experts and above (are there many?) will probably not gain much. 

An afterthought:

The author of the book is clearly passionate about the concept of vertical farms and the current non-sustainability of urban cultures. Here is a short excerpt from the book as an example:

Regardless of location, the city has grown helter-skelter, and its insatiable appetite and out-of-control metabolism produces nothing more useful than lethal bubbles of heat and contaminated air and water laced with the by-products of its mechanized infrastructure. "Metropolis" has become synonymous with "consumption." None of this negative behavior was planned, yet urbanization over the last hundred years turns out to be a thousand times more destructive than all wars put together, both in the scope of the planetary damage it has created, the number of human deaths cause by unhealthy living conditions, and its penchant for continuing to cause even more disruption of the natural world on an ever-increasing scale, as new methods for construction are established. Godzilla is a mere toddler's hand puppet compared to the way the city itself has risen up into the surrounding landscape and crushed it flat with its big foot of progress.

Energy Storage Article Published in the Journal of Applied Electrochemistry

A paper I recently authored with Robert Savinell and Walter Culver was published online last week in the Journal of Applied Electrochemistry. The article is a techno-economic optimization of an energy storage solution. Check it out!

Title
Simulation and optimization of a flow battery in an area regulation application

Abstract
Flow batteries have the potential to provide ancillary grid services such as area regulation. In this paper, a hypothetical 2 MW flow battery is simulated in an area regulation application to find the optimal energy-to-power ratio that maximizes the net present value (NPV) of a 10 year project based on a range of installation costs. Financial and operational results are presented, and candidate battery chemistries are discussed. A simplified model of battery installation costs (dollars per kWh) resulted in a positive NPV for installation costs below $500/kWh. For installation costs between $300 and $500/kWh, an optimal energy-to-power ratio is 1.39. The traditional advantage of decoupling power and energy capacity may not be realized in area regulation; therefore hybrid flow batteries may be more appropriate. Zinc-bromine and iron-chromium chemistries might fit well with this application, along with lower-cost flow battery chemistries in the future.

Citation

Reference Type: Journal Article
Author: Mellentine, James
Author: Culver, Walter
Author: Savinell, Robert
Primary Title: Simulation and optimization of a flow battery in an area regulation application
Journal Name: Journal of Applied Electrochemistry
Cover Date: 2011-06-15
Publisher: Springer Netherlands
Issn: 0021-891X
Subject: Chemistry and Materials Science
Start Page: 1
End Page: 8
Url: http://dx.doi.org/10.1007/s10800-011-0326-8
Doi: 10.1007/s10800-011-0326-8

Promoting Energy Efficiency via Utilities

In order to reduce greenhouse gas (GHG) emissions and promote a more sustainable energy culture, increasing energy efficiency should be among the primary goals for federal and state energy policy. According a to 2009 McKinsey study, implementing energy efficiency measures not only have huge potential to reduce GHG emissions, but can often do so profitably [1]. Figure 1 shows a GHG abatement curve from the study. The dark bars represent net present value (NPV)-positive efficiency strategies for stationary uses (i.e. does not include transportation energy).

Figure 1 - Greenhouse gas abatement curve published in a 2009 McKinsey report [1].

One way to implement energy efficiency measures are through utilities. Not only can they increase the efficiency of their own generation plants, but they can encourage customers to increase their own household, commercial, and industrial energy usage. However, there is a problem with this: why would the shareholders of a utility - whose returns increase as energy use increases - want to decrease the amount of energy their customers use? This is a fundamental conflict of interest that regulators and operators have been trying to overcome, and are partially succeeding through decoupling measures.

Decoupling separates a utility's revenue from the amount of energy sold, effectively removing a utility's incentive to sell more energy and disincentive to promote energy efficiency. However, decoupling does not necessarily incent a utility to invest in energy efficiency. A 2007 report from the National Action Plan for Energy Efficiency Leadership Group does a great job of outlining this issue and providing solid program examples (a few of which I mention in this post) [2]. What follows is a presentation of decoupling strategies that are being used today - these experiences should be learned from, adapted, and expanded.

Expensing Energy Efficiency Investments

This policy allows a utility to invest in energy efficiency (EE) and recoup the invested amount in the same year via rate increases or fixed charges for rate-paying customers.

Pros: This is a low-risk, revenue-neutral mechanism for EE investment

Cons: There is no profit from the EE investments, so no incentive for the utility. Also, varying annual investments could introduce rate volatility to consumers. Further, EE investments could delay or decrease the need for investments in new generation capacity, which erodes the rate base of the utility.

Example: In Iowa, EE expenses are recovered over a 12-month period and rates are adjusted annually based on over/under recovery [2].

Performance Incentives

Similar to expensing, except the utility also receives a lump sum award based on the level of EE investments against set targets.

Pros: This is a low-risk, revenue-neutral mechanism for EE investment. This also creates an incentive to invest in EE, and provides cash flow to offset rate base erosion.

Cons: There is still risk of rate volatility. Also, there may not be link between the incentive and actual energy savings.

Example: In Massachusetts (NSTAR Electric), an annual incentive is based on savings, value, and performance. If targets are met, NSTAR receives 5% of net energy savings, and a bonus payment for "exemplary performance". The incentive is approximately $2.4 Million if all goals are met [2].

Shared Savings

This mechanism is also similar to expensing, except the utility is allowed to recover a percentage of the energy savings from EE investments.

Pros: This is a low-risk, revenue-neutral mechanism for EE investment. This also creates an incentive to invest in EE, and provides cash flow to offset rate base erosion. Further, this mechanism links the incentive payment with actual energy savings.

Cons: There is still risk of rate volatility to consumers if program controls are not in place.

Example: In addition to expensing the EE investment expenses, PG&E in California receives 15% of actual energy savings. They received $33.4 Million from efficiency incentives in 2009 [3].

Capitalizing EE Investments

This policy allows a utility to invest in energy efficiency (EE) and recoup the invested amount over time plus a rate of return. The revenue is still generated via rate increases or fixed charges for rate-paying customers.

Pros: This is a low-risk, revenue-neutral mechanism for EE investment. This also creates an incentive to invest in EE, and provides cash flow to offset rate base erosion. It also decreases rate volatility since expenses are recovered over a longer period.

Cons: This mechanism does not link the incentive with actual energy savings. It can also create shareholder concerns regarding the control of rate base assets (i.e. there is perceived risk if the energy efficiency investment is not under the control of the utility) [4].

Example: Nevada Energy receives a bonus ROE for EE investments. Their programs include free refrigerator replacement and rebates on lighting, AC, heat, water pumps, insulation, and others [2]. The program has achieved an estimated savings of over 250 GWh in 2007, with a further estimated $135 Million invested between 2008-2010 [5].

Virtual Power Plant

This is similar to capitalizing, except the utility plans for specific performance requirements from the virtual power plant similar to a real power plant, and targeted efficiency applications are identified to fulfill the performance requirements. This can be accomplished at much lower cost than developing new generation capacity.

Pros: Similar to capitalizing. Since the energy savings are more thoroughly planned, the investment is also more directly linked to savings.

Cons: There might still be shareholder concerns regarding the control of rate base assets.

Example: In Jiangsu, China, a 301 MW virtual power plant was designed with an estimated investment of $134 Million ($445/kW installed). The "virtual" levelized cost of electricity is about 1 cent per kWh [6].


Conclusion

This list of policy mechanisms is not comprehensive, but are specific examples that are being (or have been) used in various markets. So, which incentive structure is best? It depends. Different markets have different needs. How much efficiency is needed or is possible? What is the current regulatory structure? How much risk is the utility shareholders or ratepayers willing to accept? More than one solution (or a hybrid solution) may be appropriate. In each case, careful analysis of each situation is warranted. The important takeaway from this is that there are effective policies in place which are significantly reducing energy demand. The lessons learned from these policies should be used to refine and adapt programs to individual markets, with continuously improving results. These policies should be widely expanded to produce even greater reductions.


References

[1] McKinsey. Unlocking Energy Efficiency in the US Economy. 2009. http://www.mckinsey.com/clientservice/electricpowernaturalgas/downloads/US_energy_efficiency_full_report.pdf
[2] National Action Plan for Energy Efficiency. Aligning Utility Incentives with Investment in Energy Efficiency. 2007. http://www.epa.gov/cleanenergy/documents/suca/incentives.pdf
[3] PG&E. PG&E Corporation Financial Reports. May 12, 2010. http://www.pgecorp.com/investors/financial_reports/annual_report_proxy_statement/ar_html/2009/index.html
[4] Lazar J. Alternatives to Decoupling. 2008. http://docs.google.com/viewer?a=v&q=cache:UinqXRbJVXAJ:www.puc.state.mn.us/portal/groups/public/documents/pdf_files/000937~1.pdf+alternatives+to+decoupling&hl=en&pid=bl&srcid=ADGEESgGVPwOZLg5L0FWk1TVUwShxFkEbtvV0hRlP62hFJjVBh-Qo2-esJfb4
[5] NV Energy. A Balanced Approach - Sierra Pacific Resources 2007 Annual Report. 2008. http://media.corporate-ir.net/media_files/irol/11/117698/SRP_AR_2007and10K.pdf
[6] Asian Development Bank. A Rapid, Low Cost Path for Energy-Saving Investments in Jiangsu. 2005. http://www.google.com/url?sa=t&source=web&cd=3&ved=0CCoQFjAC&url=http%3A%2F%2Fwww.imt.org%2FPapers%2FChina%2FEPPProspectus.doc&ei=IGJ5TI_kEti4jAff5PTDBg&usg=AFQjCNHzKt86DspbhoPaItdSHaoaSan00Q

Algal Biodiesel vs. Conventional Diesel: Comparisons and Tradeoffs

There is a lot of current research and development to push algal biofuels toward commercialization as a replacement for existing fossil fuels - namely diesel and jet fuel. But is algal biodiesel really the same as conventional diesel? As you probably know, biodiesel refers to fuels comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats [1]. In general, biodiesel has similar properties to fossil-fuel derived diesel fuel and can be used in existing diesel engines. There are, however, some key differences and tradeoffs to be considered for the use of algal biodiesel. The purpose of this post is to highlight and describe those differences.

But first, some basics - an overview of the diesel engine and fuel production processes of diesel and algal biodiesel.

Compression Ignition Engine Operation

The Compression Ignition (CI) or diesel engine operates on a four-stroke cycle similar to a gasoline engine, except that the combustion takes place via autoignition of the fuel in compressed air instead of by a spark from a spark plug. The components of the combustion system in the CI engine include an intake and exhaust valve, to allow air to flow in and exhaust gases to flow out, respectively. It has a direct fuel injector to inject fuel into the combustion chamber. The valves and injector are located in the cylinder head, which is positioned above the piston. The piston is enclosed with cylinder walls, completing the boundary of the combustion chamber. When the position travels laterally up and down the cylinder, it transfers its linear mechanical energy to rotational mechanical energy via a rotating crankshaft. Figure 1 illustrates each component of the system. 

Figure 1 - Diagram of diesel combusion system [21]

The cycle starts with the piston at top dead center (TDC). The intake valve opens as the pistons moves down the cylinder, pulling in fresh air (and possibly some recirculated exhaust as described in later sections). The next stroke begins with the piston at bottom dead center (BDC). Both valves are closed as the piston moves up the cylinder, compressing all of the air into a small space, drastically increasing its temperature and pressure. The third stroke begins as the piston approached TDC again, and the fuel injector quickly pumps fuel into the chamber. The fuel autoignites from the high temperature in the compressed air, transforming its chemical energy into heat energy. The heat energy is transformed into mechanical energy as is pushes the cylinder back down to BDC. The fourth stroke begins with the piston at BDC. The exhaust valve opens as the piston moves up the cylinder, pushing the combustion products out of the chamber. Then the cycle starts all over from the beginning. An animation of the cycle can be found here.

Production of fossil-fuel derived diesel

Conventional diesel fuel (and other petroleum products) starts as crude oil pumped from the ground. Crude oil is a mixture of hydrocarbon molecules of varying sizes. A process called fractional distillation is used to separate the molecules using their inherent nature of having different boiling points. A fractional distiller is essentially a large vertical furnace in which crude oil is heated in progressively hotter chambers, each of which route the resulting gases into separate condensers and containers. In this way diesel, gasoline, kerosene, and other oil products are separated from the crude oil feedstock. The distillation temperature for diesel fuel is in the range of  250 ^oC - 350 ^oC [2].

Production of algal biodiesel

In the case of algal biodiesel, the fuel is harvested and processed from oils contained in three main types of algae: microalgae, cyanobacteria, and macroalgae. Algae are naturally composed of three main components: proteins, carbohydrates, and lipids. It is the lipids (fatty acids) that are the source of the fuel. While there are several extraction and conversion methods currently being researched, a common method is harvesting of microalgae via filtration, drying the algae to reduce water content, pressing the resulting algae to remove the oil, and then converting the oil to biodiesel through chemical transesterification.

Analysis of Fuel Considerations

The comparison of fuels used in transportation should include a wide variety of performance indicators that have a direct impact on engines, consumers, and the environment. A fuel that seems far superior in one category could have clear disadvantages when evaluated in another category. Societies must consider these tradeoffs when investing in the infrastructure required for the mass production and distribution of transportation fuels. Here, the performance of diesel and algal biodiesel characteristics are compared in seven categories: availability, cost, ease of use, energy properties, physical properties, safety, and emissions.

Availability

According to BP, global crude oil reserves are about 1333 billion barrels [3]. According to the same source, the world is consuming over 84 million barrels of oil per day. At the current rate of consumption (and assuming no new discoveries), this reserve will last 15,855 days, or about 43 years. In addition, the majority (56.6%) of proven reserves are in the Middle East, with only 5.5% of reserves in North America [3]. This is clearly an unsustainable trend. Energy is a major factor in the average standard of living, and upcoming scarcity of fossil fuels has the potential to cause major political upheaval and regional conflict in the next few decades. In the short term, diesel fuel is widely available (at least in the developed world). All gasoline stations have pumps dedicated to diesel fuel, and a widely developed infrastructure exists to produce and distribute diesel fuel to stations and consumers.

On the contrary, biodiesel derived from algae is not yet commercially available on a widespread basis, even as millions of research dollars and many young start-up companies are trying to develop cost-effective production methods. It is noteworthy that the US Navy recently purchased 1500 gallons of algal jet fuel for testing and certification [4]. Unlike traditional biofuel feedstocks which require lots of land and fresh water, algae is unique in that it doesn’t have to be grown on arable land or require much fresh water. Algae can be grown in bioreactors on arid or non-arable land or in large farms offshore. It can also be grown in brackish water. This means that it can be produced locally or regionally. This benefit would reduce the world’s reliance on a few nations for oil and reduce the need to transport crude around the world. If and when biodiesel from algae is ramped up to larger scale production, it could be distributed using the existing diesel infrastructure.

Although biodiesel yields vary by species, environment, and location, here is a rough order of magnitude calculation to determine how much area might be required to grow enough algae to replace all diesel consumption in the US. In 2008, the US consumed over 41 billion gallons of diesel for on-road transportation [5]. According to a recent study, producers can practically expect a yield of about 4350 – 5700 gallons per acre-year from algae [6]. Dividing 41 billion by this yield range shows that 10,900 – 14,400 square miles would be required to produce enough biodiesel to replace all on-road transportation needs in the US. This is roughly the size of the state of Maryland.

Cost

The cost of conventional diesel fuel in the last 16 years has ranged between $1/gallon and $4.70/gallon, with the current price just under $4/gallon. Figure 2 shows the pump price of diesel fuel from June 1994 through March 2011 [7].

Figure 2 - Average pump price of diesel fuel in the U.S. from June 1994 through March 2011 [7]

While the price has been volatile in recent years, it is still less than biodiesel production from algae. Since there are no large-scale production facilities of algal biodiesel, an accurate comparative cost per gallon is difficult to estimate. Some rough estimates put the current production price at around $50/gallon [8]. However, an anecdotal comparison can be made to algal jet fuel, which is farther along the path to commercialization. In February 2010, the Defense Advanced Research Projects Agency (DARPA) announced plans to build a large-scale algal jet fuel facility by 2013. It expects the production price to be under $3/gallon [9]. If this becomes a reality, and similar large-scale operations could be developed to produce biodiesel, it will be competitive in the marketplace.

Ease of Use & Compatibility

Since biodiesel fuel can be provided to the customer through the existing diesel infrastructure, there would be no difference in convenience or refueling time to a consumer.

Since most newer diesel engines are designed to accept low-sulfur diesel fuel and biodiesel blends up to 20% (B20), most consumers can use biodiesel in their existing diesel engines without any modification. However, in higher percent blends like B100, it is possible that certain natural rubber seals or hoses could degrade at an increased rate [10]. People who make the switch to B100 should check with the manufacturer to determine if any engine modifications are necessary. However, if it becomes clear that biodiesel is becoming more common in the marketplace, auto makers will inevitably start considering that in the design process so that diesel engines would be able to accept B100 blends with no modification.

Energy Properties

Energy-related properties of biodiesel should be considered when comparing to conventional diesel. One of the most important properties is cetane number. This is the measure of a fuel’s ignition delay, or the amount of time between the start of fuel injection and the start of combustion. A higher cetane number corresponds to a shorter ignition delay, so for diesel fuel a higher cetane number is generally better, since a shorter ignition delay will increase the cutoff ratio α and thus increase engine efficiency based on the equation for diesel cycle thermal efficiency:

The cetane number in conventional diesel varies between 40 and 45 in the US. The cetane number in biodiesel depends on feedstock, but usually varies between 45 and 67 [11]. A recent study of algal biodiesel reports a cetane number of 52 [12]. The increased cetane number in algal biodiesel will have a positive effect on engine efficiency.

Another important property of a fuel is its energy density. This matters because the higher the energy density, the better the fuel economy one can expect from the fuel, and the longer the range that can be achieved per tank. The energy density of conventional diesel is about 43.1 MJ/kg, or 35.9 MJ/L [13]. For biodiesel, this property also varies by feedstock. The same recent study of algal biodiesel reports an energy density of 40 MJ/kg, or 32.04 MJ/L [12]. This is about 7% less energy by mass, or 11% less by volume than conventional diesel. Some proponents of algal biodiesel report that some of these energy losses are offset by the higher combustion efficiency and better lubricity such that overall fuel economy (and range) is only decreased by 2% [14]. If this is true than decreases in fuel economy and range from algal biodiesel would be barely noticeable to the average driver.

I also performed some detailed calculations surrounding the adiabatic flame temperature of combustion in each fuel. The thermodynamics can get a little eye-glazing, so I’m not including the details – but they are here if you are interested. In summary, the flame temperature of conventional diesel is 2831 K, while the flame temperature from algal biodiesel is only slightly higher at about 2855 K. In theory, this slight increase in temperature indicates a slightly higher increase in efficiency, and might also result in increased NOx emissions (since NOx are formed in atmosphere at high temperatures). However, the relative temperature difference is so small that an actual difference in efficiency and NOx emissions may not be measurable.

Physical Properties

There are some important physical characteristics of biodiesel that should be considered when comparing with conventional diesel fuel. These properties include lubricity, API gravity, and cloud point.

In diesel engines, the fuel is what lubricates the fuel injection pumps and injectors. The lubricity of a fuel is the measure of the wear or scarring that occurs between two metal parts covered with the fuel as they contact each other. Better lubricity results in less wear and scarring. Lubricity is generally measured by the wear scar diameter (WSD) that results on a specific test rig. The lubricity of conventional diesel is 536 microns, whereas B100 has been measured at 314 microns, an indication of better lubricity [15].

The API gravity and its inverse specific gravity are basically a measure of fuel density, and can be used to provide an indication of how the density of a fuel varies with temperature. Studies have shown that the density of biodiesel varies in a linear fashion that is very similar to conventional diesel [16].

The cloud point is the temperature below which wax molecules in the diesel fuel begin to solidify, potentially resulting in gelling of the fuel. Gelling is a serious functional problem since it reduces or eliminates the ability of the fuel to flow through the injection system – essentially not allowing the engine to run. The cloud point of conventional diesel varies, but can be as high as -15 ^oC. Fuel additives, electric engine block or fuel warmers, and heated garages are commonly used in colder climates to work around this problem. The cloud point in biodiesel also varies, but is generally higher than conventional diesel. A recent study shows the pour point of algal biodiesel to be -14 ^oC, which corresponds to a cloud point of about -11 ^oC to -8 ^oC [12]. A switch to algal biodiesel would require the adoption of the same workarounds to a wider section of the population.

Safety

Safety is obviously an important consideration when analyzing a fuel. Important measures of fuel safety are its stability, flame visibility, and flash point.

Fuel stability can refer to thermal, oxidative, and storage stability. The most common comparison between biodiesel and diesel is oxidative stability, or the tendency of the fuel to react with oxygen at near-ambient temperatures. Biodiesel is more prone to oxidation because of the increased proportion of carbon-carbon double bonds. Oxygen atoms can more easily bond with adjacent carbon atoms, forming a hydroperoxide molecule. This reaction reduces molecule chain length, which can reduce the flash point, cause undesirable odors, and cause the formation of sediments in the fuel. ASTM D2274 test standards are usually used to measure stability in diesel fuel. However, this test is not adequate to measure biodiesel stability because of its incompatibility with the filters used in the test [17].  This instability should continue to be a focus of improvement for biodiesel. Stability can be improved through the manufacturing process and by the use of fuel additives or blends [18].

Flame visibility is simply how well you can see a flame resulting from the combustion of a fuel. It is more commonly a concern in industrial environments. The literature on flame visibility of diesel and biodiesel is thin. This suggests that there is likely not much of a difference in this factor.

At ambient temperatures, a fuel can mix with the surrounding air and become ignitable, causing a serious safety concern. The temperature at which this mixing begins to occur is called the flash point. A higher flash point is safer. The flash point of conventional diesel fuel is 52 ^oC [19]. The flash point of algal biodiesel is around 98 ^oC [12]. Biodiesel is therefore better in regards to the flash point, presenting a very low fire hazard.

Emissions

With so many vehicles on the road, tailpipe emissions are important to consider since they influence human health, quality of life, and global warming. The EPA produced a report in 2002 that compared emissions of various blends of biodiesel with conventional diesel. For B100, they found that biodiesel produced 67% less hydrocarbons, 48% less carbon monoxide, 47% less particulate matter, 80% less polyaromatic hydrocarbons, and 10% more NOx [20]. Figure 3 is from the EPA report and shows the relation between emissions and biodiesel blend percent.

Figure 3 - The effect on exhaust emissions for a range of biodiesel blends [20]

Biodiesel also produces no sulfate emissions since it does not contain sulfur, unlike conventional diesel. The higher oxygen content in biodiesel results in a higher combustion efficiency, which increases the combustion temperature and thus increases the amount of NOx emissions, since NOx are only formed above approximately 1500 ^oC. The CO₂ emissions from biodiesel combustion are the same as that from conventional diesel. However, since the CO₂ in biodiesel was captured through the process of photosynthesis in the feedstock, the algal biodiesel has an overall life-cycle CO₂ impact that is less than conventional diesel, assuming the CO₂ emitted in the processing of the biodiesel is less than the CO₂ saved. The relative value of each emission species is debatable, but overall the biodiesel has a clear advantage when it comes to emissions.

Regardless of the fuel used in a vehicle, there are two basic ways to reduce emissions: pretreatment or aftertreatment. It is noteworthy that diesel engines have traditionally not been treated, and therefore have higher polluting emissions than gasoline engines. In the last decade, the US has implemented low-sulfur regulations in diesel. Now all diesel fuel must meet the standard of having less than 15 ppm of sulfur. This is an example of pretreatment, where pollutants are removed from the fuel before it is burned. Another example of pretreatment is exhaust gas recirculation (EGR), where a portion of the exhaust stream is routed back into the intake of the engine and fed into the combustion chamber. This has the effect of lowering the flame temperature of the combustion event. Exhaust gas is able to absorb more heat energy from the combustion event than air since it is composed of inert triatomic molecules. This technology is common in diesels manufactured today. Another technology that increases the combustion efficiency and reduces pollutants is better fuel injection technology that uses higher pressures and pulsed injection, helping the fuel mix with the air more rapidly and evenly. Aftertreatment is when pollutants are removed after combustion, in the exhaust stream. One potential aftertreatment device for diesel engines are particulate matter traps. This comes with a tradeoff in efficiency and cost since traps block the flow of exhaust gases, thus the need for two separate traps and a mechanism to switch between the two when one is sufficiently full and needs to have the particulates burned off. Another potential aftertreatment method involves the addition of urea to the exhaust gas stream, followed by a Selective Catalytic Reduction (SCR) converter. Through a complex series of reactions, the “doping” urea and the catalyst turn much of the NOx emissions into water and nitrogen.

Conclusions

Based on this analysis, it is my opinion that the advantages of algal biodiesel outweigh the disadvantages, and that it shows promise as a replacement for conventional diesel fuel. Additional research and development should continue.

While not yet commercially available, algal biodiesel can use the same infrastructure as the existing diesel distribution network. And the potential for domestically sourced feedstock is a major advantage in order to avoid political instability and potential regional conflict due to scarcity of petroleum resources. While the technology is not fully commercialized, it has been shown that full-scale production of algal biofuel can be cost-competitive with conventional diesel.

The higher cetane number of biodiesel will increase the efficiency of the engine, while the lower energy density of the fuel will cause a very small decrease in fuel economy. The higher flame temperature in biodiesel combustion will slightly increase engine efficiency. Biodiesel is also much less of a fire hazard. A significant disadvantage of biodiesel is low-temperature performance and oxidative instability. While these factors are not significant enough to prevent wide adoption of biodiesel, further research should be conducted to help reduce or eliminate these drawbacks.

Finally, biodiesel has a clear advantage in terms of exhaust emissions. The only species that it performs worse than diesel is in NOx. Implementation of mentioned aftertreatment technologies can help reduce these and other emissions, along with further research to improve diesel engine emissions performance.

Works Cited

[1] NBB. The Official Site of the National Biodiesel Board. 2010. http://www.biodiesel.org/resources/definitions/default.shtm 

[2] HowStuffWorks. How Oil Refining Works. http://science.howstuffworks.com/environmental/energy/oil-refining2.htm 

[3] BP. Statistical Review of World Energy 2010. BP, 2010.

[4] Lane, Jim. Biofuels Digest. August 10, 2010. http://biofuelsdigest.com/bdigest/2010/08/10/solazyme-takes-lead-in-race-for-commercialized-algal-oil-raises-52m-for-algal-fuel-expansion/ 

[5] EIA. Estimated Consumption of Vehicle Fuels in the United States. April 2010. http:// www.eia.doe.gov/cneaf/alternate/page/atftables/attf_c1.xls 

[6] Weyer, K., D. Bush, A. Darzins, and B. Willson. "Theoretical Maximum Algal Oil Production." Bioenergy Research, 2009: 204-213.

[7] EIA. Independent Statistics and Analysis. August 2010. http://www.eia.doe.gov/oog/info/wohdp/diesel.asp 

[8] Doty Energy. Micro-algae. May 5, 2010. http://www.dotyenergy.com/Markets/Micro-algae.htm 

[9] Goldenberg, Suzanne. Algae to solve the Pentagon's jet fuel problem. February 13, 2010. http://www.guardian.co.uk/environment/2010/feb/13/algae-solve-pentagon-fuel-problem 

[10] NBB. Biodiesel Performance. 2010. http://www.biodiesel.org/pdf_files/fuelfactsheets/Performance.PDF 

[11] Van Gerpen, Jon. National Biodiesel Board. September 1996. http://www.biodiesel.org/resources/reportsdatabase/reports/gen/19960901_gen-187.pdf 

[12] Vijayaraghavan, K. , Hemanathan, K. "Biodiesel Production from Freshwater Algae." Energy Fuels, 2009: 5448-5453.

[13] EUCAR. Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context. March 2007. http://ies.jrc.ec.europa.eu/uploads/media/TTW_Report_010307.pdf 

[14] Oilgae. Algal Biodiesel Characteristics & Properties. 2010. http://www.oilgae.com/algae/oil/biod/char/char.html 

[15] NBB. Lubricity. 2010. http://www.biodiesel.org/pdf_files/fuelfactsheets/Lubricity.PDF 

[16] Tat, M., Van Gerpen, J. "The Specific Gravity of Biodiesel and its Blends with Diesel Fuel." Journal of the American Oil Chemists' Society, 2000: 115-119.

[17] Becon. Fuel Stability. http://www3.me.iastate.edu/biodiesel/Pages/biodiesel19.html 

[18] Kenreck, Glenn. "Improving Biodiesel Stability with Fuel Additives." Biodiesel Magazine, February 2007.

[19] Engineering ToolBox. Flash Point - Fuels. 2005. http://www.engineeringtoolbox.com/flash-point-fuels-d_937.html 

[20] EPA. A Comprehensive Analysis of Biodiesel Impacts on Exhaust Emissions. Ann Arbor, MI: US Environmental Protection Agency, 2002.

[21] DOE. "Just the Basics - Diesel Engine." US Department of Energy - Office of Energy Efficiency and Renewable Energy. August 2003. http://www1.eere.energy.gov/vehiclesandfuels/pdfs/basics/jtb_diesel_engine.pdf

- EIA. What fuels are made from crude oil? http://www.eia.doe.gov/kids/energy.cfm?page=oil_home-basics#oil_refining-basics 

- NFCRC. National Fuel Cell Research Center - dynamic analyses and control. 2009. http://www.nfcrc.uci.edu/2/ACTIVITIES/RESEARCH_STUDIES/Dynamic_Analyses_and_Control/Planar_and_Tubular_Solid_Oxide_Fuel_Cells/Index.aspx 

- Reed College. The Last Chem 101 Conference. November 30, 2005. http://academic.reed.edu/chemistry/courses/chem101_05/conference/Conf11ThermoSolns.pdf 

- World Energy Council. 2007 Survey of Energy Resources. London, United Kingdom: World Energy Council, 2007.

- Yu-jie Fu, Yuan-gang Zu, Li-li Wang, Nai-jing Zhang, Wei Liu, Shuang-ming Li,. Determination of Main Fatty Acid Methyl Esters in Biodiesel Product from Yellow Horn. Harbin, China: Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, 2007.