Requesting Feedback on Renewable Diesel Essay

As some of you may know, I am writing the renewable diesel chapter for a book on renewable energy. My submission is due at the end of July. The chapter is well underway, but I have a nagging feeling that I am forgetting to address something. So, I wanted to share the outline I have, and see if anyone has any comments. If you know of a substantial feedstock that I have missed, or can think of some things you think should be covered in a specific section, let me know.

For instance, in the section on environmental considerations, I am going to point out that tropical forest is being cut down to produce palm plantations for palm oil. On the other hand, biodiesel, unlike petroleum diesel, is non-toxic. What else? Are there specific, little known facts about rapeseed oil that I should include? Just things like that. Basically, if you were reading a comprehensive story about renewable diesel, what specifically would you hope to see covered? To my knowledge, what I am writing has not been comprehensively covered before. I don’t know of any other work that has an extensive compare/contrast between biodiesel, SVO, green diesel, etc. I think many people hear “biodiesel”, and think it’s all the same.

The intent here is to provide a completely objective view of renewable diesel as an option in the future. I will cover pros and cons. As I said, the chapter is well underway, and I have portions of all sections done. But I just want to make sure I haven’t overlooked anything major. I can’t share any of the actual writing, as one stipulation is that this material may not have been published elsewhere. But here is the outline I have at the moment:

Renewable Diesel

Straight Vegetable Oil (SVO)


  • Definition/Production Process
  • Fuel Characteristics
  • Energy Return
  • Glycerin Byproduct

Green Diesel

  • Definition/Production
  • Hydroprocessing
  • Gasification/Fischer-Tropsch


  • Soybean Oil
  • Palm Oil
  • Rapeseed Oil
  • Jatropha
  • Algae
  • Animal Fats

Environmental Considerations

19 thoughts on “Requesting Feedback on Renewable Diesel Essay”

  1. Obviously the reader will want to see (or see citations that would enable them to find) the best long-term studies of engine performance using these various fuels.

    Also, engines (if any) where these fuels cannot be used.

    Emissions spectrum from each one: NOx, SOx, CO, CO2, VOCs, PMs …

    EROEI for each, including block heaters if/where required

  2. Several issues:

    1) Generations broadly defined, in their energy return ratios, feedstock requirements, CO2 savings, well-to-wheel analyses and scaling.

    I wish there was a meta-study, but I’ve only found one for bio-ethanol:

    2) Analysis of some of the “best of breed” 2nd gen bio-diesel models.

    There are many others to choose from. I don’t know what is the best.

    Many seem to be touting Fischer-Tropsch Biomass-To-Liquids as the holy grail for now.

    3) Bridge technologies between 1st and 2nd gen.

    NexBTL could be an example:

    4) Forest biomass issues (once we achieve 2nd gen biodiesel from wood biomass).

    Wood and esp. paper industry is worried about potential biomass competition from forest sources.

    All slides for biofuels show that they’d be using “wood residue” for biofuel production, but the best plants are designed to be more of omnivores. They could also eat the main wood biomass and bark.

    Paper companies are afraid of price competition in the forest biomass sector between the biofuel makers, if prices tend to rise for biofuels while paper prices drop.

    They are afraid biofuels will mess up their value chains.

    Everybody knows that those who can secure access to available feedstock, will win the biofuel competition.

    Will there be other potential casualties other than animal feedstock, cereals and wood for paper industry?

    You can find some stuff on this (like calculations from some of the big forest/paper industry consultancy companies).

    5) The North vs South divide for biomass production. Both UN and IEA have raised an issue on this. IEA says growing biomass for biofuels in EU zones is idiocy and advocates growing in Latin America & Africa. This can quickly become a Southern food vs Northern fuel war, as both UN and Lester Brown have warned.

    6) Sustainability of biofuel feedstock sources and the effectiviness of various certification schemes (RSPO, RTSO). That is, how high can you scale the feedstock, without resorting to slave labor, rain forest cutting or total soil depletion. Do the certifications really work right now (instead of some unknown time in the future)?

    7) Total combined biofuel potential as a percentage of world total oil/diesel consumption (IEA & Wood MacKenzie both have estimates). This should give people some perspective.

    8) Co-production potential (CHP + BTL, BTL + wood liquors, BTL + wood pellets, etc). Does it improve the situation at all?

    9) Logistics. Central vs. distributed? Optimal production unit size & placement?

  3. Hi

    Here in Finland I’ve seen some reports that one should have 3 to 5 year rotation for rapeseed fields to prevent some rapeseed diseases to get a too good hold.

    There is also a study ongoing about something like 40% loss of the crop in some locations.


  4. If you haven’t already thought of including it — you might mention thermal depolymerization (using a variety of wastes as feedstock) as discussed briefly here at the link below, in your “green diesel” section.

    Not that this is a really fully-developed process at this time, but it sounds like it has good potential.

  5. ever considered hemp? it’s not a food crop (at least the oil and seeds aren’t widely used for food now), and requires neither intense cultivation nor fertilization, basically just plant the crop so that plants are situated so as to encourage seed production. Here’s something I found from a googlesearch:
    Oil content, tocopherol composition and fatty acid patterns of the seeds of 51 Cannabis sativa L. genotypes
    Auteur(s) / Author(s)
    KRIESE U. (1) ; SCHUMANN E. (1) ; WEBER W. E. (1) ; BEYER M. (2) ; BRÜHL L. (3) ; MATTHÄUS B. (3) ;
    Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)
    (1) Institute of Plant Breeding and Plant Protection, Martin Luther University, Halle Wittenberg, Ludwig Wucherer Str. 2, 06108 Halle/Saale, ALLEMAGNE
    (2) Institute of Phytopathology, Christian Albrechts University Kiel, Hermann Rodewald Str. 9, 24118 Kiel, ALLEMAGNE
    (3) Institute for Lipid Research, Federal Research Center for Nutrition and Food, Piusallee 68/76, 48147 Münster, ALLEMAGNE
    Résumé / Abstract
    The oil content, the tocopherol composition, the plastochromanol-8 (P-8) content and the fatty acid composition (19 fatty acids) of the seed of 51 hemp (Cannabis sativa L.) genotypes were studied in the 2000 and 2001 seasons. The oil content of the hemp seed ranged from 26.25% (w/w) to 37.50%. Analysis of variance revealed significant effects of genotype, year and of the interaction (genotype x year) on the oil content. The oil contents of the 51 genotypes in 2000 and 2001 were correlated (r = 0.37**) and averaged 33.19±1.45% in 2000 and 31.21±0.96% in 2001. The γ-tocopherol, α-tocopherol, δ-tocopherol, P-8- and β-tocopherol contents of the 51 genotypes averaged 21.68 ± 3.19, 1.82 ± 0.49, 1.20 ± 0.40, 0.18 ± 0.07 and 0.16 ± 0.04 mg 100g[-1] of seeds, respectively (2000 and 2001 data pooled). Hierarchical clustering of the fatty acid data did not group the hemp genotypes according to their geographic origin. The γ-linolenic acid yield of hemp (3-30 kg ha[-1]) was similar to the γ-linolenic acid yield of plant species that are currently used as sources of γ-linolenic acid (borage (19-30 kg ha[-1]), evening primrose (7-30 kg ha[-1])). The linoleic acid yield of hemp (129-326 kg ha[-1]) was similar to flax (102-250 kg ha[-1]), but less than in sunflower (868-1320 kg ha[-1]). Significant positive correlations were detected between some fatty acids and some tocopherols. Even though the average content of P-8 in hemp seeds was only 1/120[th] of the average γ-tocopherol content, P-8 content was more closely correlated with the unsaturated fatty acid content than γ-tocopherol or any other tocopherol fraction. The average broad-sense heritabilities of the oil content, the antioxidants (tocopherols and P-8) and the fatty acids were 0.53, 0.14 and 0.23, respectively. The genotypes Fibrimon 56, P57, Juso 31, GB29, Beniko, P60, FxT, Félina 34, Ramo and GB 18 were capable of producing the largest amounts of high quality hemp oil.
    Revue / Journal Title
    Euphytica (Euphytica) ISSN 0014-2336 CODEN EUPHAA
    Source / Source
    2004, vol. 137, no3, pp. 339-351 [13 page(s) (article)] (30 ref.)
    Langue / Language

  6. Hi Robert,

    Please include a good discussion of the following two items:
    – The energy return of bio-diesel, and then a discussion that takes really all the relevant factors into account. Is bio-diesel indeed giving a net energy return or not?
    – the possible impact of the use of bio fuels on prices of food. I just read in a news paper that the price of wheat has gone up a factor of two in the last few years and that bio fules are the biggest culprit of that! (see for instance

    Rgds, John Schmitz

  7. Robert:

    Although I suspect that it is exceptionally expensive for the individual and that you are likely already familiar with it, IMO one of the most useful literature search systems is Thomson ISI’s on-line Web of Science.

    It is essentially the digital version of the evolution from the old paper Science Citation Index and Current Contents. Truly a web, its power is the linkage through the references for each indexed paper to other papers so that one can identify all the papers that have cited a particular paper or that were cited by it. Once one has several key papers in an area, one can track forward to the citing papers or back to the cited papers and from them again forward.

    Because it is so powerful as a literature search tool, I suspect that groups somewhere in most large companies and most research universities have access to it. For those who don’t have personal access, I’d suggest visiting the friendly research librarians at your nearest college campus. To help the process along, bring a list of some good papers from the primary scientific literature that are relevant to your quest.

  8. Robert-

    this may be of interest

    University of Wisconsin Engineers Develop Higher-Energy Liquid-Transportation Fuel from Sugar

    A University of Wisconsin press release, announced that university chemical and biological engineering Professor James Dumesic and his research team have developed a two-stage process for turning biomass-derived sugar, fructose, into 2,5-dimethylfuran (DMF), a liquid transportation fuel with 40 percent greater energy density than ethanol, similar to that of gasoline.

    By engineering sugar through a series of steps involving hydrochoric acid and copper catalysts, salt and using butanol as a solvent, UW-Madison researchers created a path for a sustainable, carbon-neutral fuel to reduce global reliance on fossil fuels.

    Not only does dimethylfuran have higher energy content than ethanol, it also addresses other ethanol shortcomings. DMF is not soluble in water and therefore cannot become contaminated by absorbing water from the atmosphere. DMF is stable in storage and, in the evaporation stage of its production, consumes one-third of the energy required to evaporate a solution of ethanol produced by fermentation for biofuel applications.

    Dumesic and graduate students Yuriy Roman-Leshkov, Christopher J. Barrett and Zhen Y. Liu developed their new catalytic process, reported in the June 21 issue of the journal Nature, for creating DMF by expanding upon earlier work, previous post.

    Continue reading “University of Wisconsin Engineers Develop Higher-Energy Liquid-Transportation Fuel from Sugar” »

  9. A feedstock missing from the current list: corn oil. Easily up to 50 gallons diesel equivalent per acre. At 4% (standard) to 8% (high-oil) corn’s not an oil crop, but total biomass yields are so high compared to soybean that they eventually add up. Add the efficiencies of integration with existing dry and wet-milling and you have a winner. At the very least the farm communities and shipping fleets won’t need to import much diesel fuel from half-way around the world. As for feeding efficiency – “feed the world” stuff, oil in grain, especially spent grain, doesn’t contribute to net lean meat production. What small amount of bypass oil doesn’t get fermented away as methane or microbial biomass simply contributes to intestinal hypertrophy and fatty tissue deposition in the gut along with body heat generation. Humans can also do without the fat as well.

    Production not specifically listed, but could be included under hydroprocessing: decarboxylation of fatty acids to alkanes (green diesel). Standardised aviation fuel, winterized fuel and backwards-compatability with installed fleet.

    Also would include the catalyst-free, quick supercritical alcohol esterfication of vegetable oil methods as well as the micro-reactor devices being developed.

    Pardon my online nic. 😉

  10. Are you aware that it has been discovered that the glycerol by-product produced from bio-diesel can be turned into ethanol by adding E-coli in an anerobic environment. Now that is a lot of bang for the buck!

  11. Robert,
    Have you ever studied the potential for using native hybrid perennial brush plants such as the american hazelnut to grow oil, food, and coppice.
    I think a really big part of the problem is that the crops must be well adapted to a given ecosystem to see a long term positive net energy balance.
    Most of midwest america used to be oak hazel savannah. The fires of this period would shift the land from woodland to grassland to a brush succession. The bursh succession is thought to have the highest net calorie production, why not mimic it?
    Here is one grower how is doing so with good results. He claims an average of 2000 lbs nuts per acre with a 7 year coppice period that will also yield significant biomass for cellulosic ethanol or gasification purposes. Some of the big advantages are low to no inputs and good disease resitance.
    I know some farmers currently growing this crop looking for avenues to develop it further. If you are interested I can get you much more infromation. Either way thanks for your great work.

    Nick Raaum

  12. Regarding Requesting Feedback on Renewable diesel.

    It is incorrect to say that “On the other hand, biodiesel, unlike petroleum diesel, is non-toxic.” Although biodiesel is more biodegradeable than petroleum it does have significant toxicity if spilled. e.g. oil spilled on water would be very harmful to birds and marine life.

    Also, because if does not contain some of the highly toxic compounds in petroleum available information suggests significant toxicity from particulate emissions.

  13. The key issue for me with all crop based fuel systems is the effect that they have on food production and on the rest of the natural world.

    Any fuel system (e.g. ethanol from corn [maize])that threatens to starve people in the third world must be reckoned as morally offensive.

    Furthermore we should not kid ourselves if we think that we are replacing a non-renewable resource like petroleum with a crop, if the production of that crop is simply depleting other non-renewable resources such as the soil.

    I have attempted to research the input issues raised by canola; i.e. how much fertilizer and how much irrigation does its production require and I came up dry. But Google can be a blunt instrument at times.

    By my criteria we should be looking at perennials instead of annuals, preferably ones that would do well with out irrigation or fertilizer. Further, we should avoid invasive crops. No purple loosestrife please.

    Jatropha is the type of plant that we should be looking for. Another one is the olive. Whether enough of any type of oil producing plant can be raised without grossly distorting land use patterns is a good question.

  14. I don’t really have very much to add, but one thing that I have noticed in most academic coverage of potential feedstocks is an unwillingness to deal with market dynamics. You have to deal with the commodity price of a good, not the production cost. It’s not meaningfully predictable, but researchers could do a better job of adverting to how mkt dynamics will shift cost structures.

  15. Here’s another facet that is rarely considered concerning biodiesel: emissions control technology. Although biodiesel obviously burns cleaner (with the exception of NOx emissions) than regular diesel, it still creates emissions through incomplete combustion that can be further reduced with the use of diesel particulate filters. Particulate matter, hydrocarbons and carbon monoxide are virtually eliminated with diesel particulate filters which can reduce emissions from regular diesel by between 85% to 99%. Underground mining operations, as well as some stationary engines used for power generation are moving towards a biodiesel blend AND retrofitting equipment with filters to further decrease emissions.

    For more info on emissions control technology visit

  16. note that methanol is a feedstock for dimethylether (DME), which can be used in diesel engines. Methanol can be produced from CO2 in flue gas, so it could be an alternative to CO2 sequestration in coal-fired power generation plants. Prof George Olah has a book out about this process:
    Beyond Oil and Gas: The Methanol Economy (Hardcover)
    by George A. Olah (Author), Alain Goeppert (Author), G. K. Surya Prakash (Author)

    and has published an essay:
    “Beyond Oil and Gas: The Methanol Economy”, George A. Olah, Angewandte Chemie International Edition Volume 44, Issue 18, Pages 2636-2639, 2005

    this is from

    About Methanol

    I recently read two related articles regarding methanol which were somewhat conflicting and perked my interest in methanol. The first was the announcement of a new plant for producing methanol.

    Methanol Holdings (Trinidad) Limited (MHTL) announced that its M5000 methanol plant achieved first methanol production on September 23, 2005 and expected to achieve full production of 5400 tons per day, making it the largest methanol plant in the world, during the first week of October. The total production capacity of MHTL’s four plants is now about 4 million metric tons per annum (11,000 tons per day).

    My immediate naive reaction was that converting stranded natural gas to methanol was an inexpensive way, less expensive than FT synthesis, to convert the gas to a liquid which would make the transportation much less complex (stranded gas refers to gas that is not in sufficient supply to justify converting it to LNG). Methanol could be used as a vehicular fuel, so there should be a market for it. Shortly after I saw the above announcement I saw an article in the Oil & Gas Journal about an overcapacity situation in methanol. According to the article:

    During its 5-year study period, beginning in 2006, CMAI in its 2006 World Methanol Analysis, forecasts world demand for methanol to be about 38 million tonnes/year. Meanwhile, nearly 27 million tpy of new capacity is planned for the same period and most expansions are not demand-driven, it said.

    The largest absolute growth for methanol will be fueled by the Middle East and Northeast Asia, most notably China, as this country continues to build infrastructure to support its economic development.

    Methanol demand in North America will decline as the methyl tertiary butyl ether phase-out programs sweep the US by 2007. This will eliminate the use of 9 million tonnes of MT BE by 2008, the equivalent of more than 3 million tonnes of methanol. Also, Europe is rapidly replacing MT BE with biofuels. It is expected to reduce MT BE production by 1.8 million tonnes (about 600,000 tonnes of methanol) from the 2000 peak consumption time frame to the end of the study period.

    CMAI said the probability is high for the planned methanol-to-olefins complex in Nigeria in 2009. This addition, which will interact independent of the methanol industry and derivatives, will create almost 2.2 million tonnes of new demand.

    Methanol is the simplest alcohol and has a chemical formula of CH3OH. It is clear and colorless but has a characteristic pungent odor. It is a volatile and flammable liquid and may be fatal or cause blindness if swallowed. Hence, it is certainly not a drinking alcohol but rather an extremely versatile industrial chemical used in the manufacture of a wide range of raw materials including Formaldehyde, MTBE, Acetic acid Dimethyl Terephtalate (DMT), Methyl Methacrylate (MMA) Methyl amines, fuel, and antifreeze. These are used to make a wide variety of products such as plastics, solvents, dyes, glues, wood products, polyester fibers and fabrics for clothing.

    Developing markets for methanol are in fuel cells as the source of hydrogen and as a precursor for olefins; benzine, butadine, ethylene, propylene, styrene and toluene; which are some of the most important building blocks of the petrochemical industries and used to make such consumer products as plastics, packaging, automobile parts, small appliances, carpet backing, synthetic rubber and nylon fibers.

    The use of methanol as a vehicular fuel intrigued me and I found these arguments for its use as proposed by Vanderzee:

    * The world-wide energy crisis is driven by the cost and availability of gasoline.
    * The U.S. has a 200+ year supply of usable fuel in the form of coal.
    * We can convert coal to methanol using proven technology in “zero discharge” plants.
    * Methanol is a high performance motor fuel – just ask the Indy car drivers.
    * Methanol can be stored in tanks, transported by pipeline or tanker and pumped into our cars just like gasoline, which minimizes conversion costs for our fuel infrastructure.
    * Auto manufacturers can produce methanol engines at the same cost as gasoline engines.
    * Methanol is not a threat to groundwater, per the EPA.
    * We can build coal to methanol plants in Illinois, Ohio, Kentucky, and West Virginia – creating jobs in regions that need investment.

    Zumerchik has this to say about this subject:

    Automobiles that are designed to run on methanol need a few modifications to become flexible fuel vehicles (vehicles that run on either gasoline or methanol). First, for the fuel tank, fuel lines and fuel-injection equipment, the vehicle needs noncorrosive materials such as stainless steel and high-fluorine elastomers. Second, since methanol is a lower energy density fuel, fuel injectors must be larger to provide greater volumes of fuel, and vehicles must be equipped with larger fuel tanks to achieve a range comparable to a gasoline vehicle. Third, a fuel sensor that detects fuel composition is needed to relay information to the on-board computer. And finally, the lower volatility and higher heat vaporization of methanol requires a special starting system for convenient cold weather start-ups.

    I found other sources that said that special starting systems were not needed unless the methanol concentration was greater than 85%. It sounds to me that, except for the fuel sensor that detects fuel composition, which is not necessary to run ethanol, a car that can run methanol can run ethanol. There are thousands of cars running on M85 methanol in California to meet stringent emissions standards and I found a large fleet running on methanol in Arizona.

    There are a couple of safety concerns with methanol because it is very poisonous and the fact that when it burns the flames from pure methanol are colorless, but fires are easier to put out than gasoline fires. There have been several reports of the corrosiveness of alcohols when used in standard diesel engines.

    EPA has found that the efficiency of methanol fueled engines was 33% higher using 100% methanol rather than gasoline, while ethanol had 25% higher efficiency than gasoline in advanced high efficiency engines.

    With our large coal reserves making methanol from coal would be less expensive than making diesel or gasoline from coal. A 2004 DOE report (p 6) indicated that methanol could be made from coal for $0.50 per gallon. The tests for this study were made at a Tennessee Eastman chemical plant that was already gasifying coal to produce chemicals. The $0.50 per gallon figure was obtained assuming methanol was coproduced from an IGCC plant. Making methanol from biomass is also possible, competitive with gasoline according to a ALTENER report, but more expensive than making it from coal. ALTENER studied the gasification of black liquor to make methanol, a process also being studied by the U.S. DOE.

    Production of methanol from natural gas as practiced by MHTL is broken down into four steps:

    1. FEED PURIFICATION – The two main feedstocks, natural gas and water, both require purification before use. Natural Gas contains low levels of sulfur compounds and undergo a desulfurization process to reduce, the sulfur to levels of less than one part per million. Impurities in the water are reduced to undetectable or parts per billion levels before being converted to steam and added to the process. If not removed, these impurities can result in reduced heat efficiency and significant damage to major pieces of equipment.
    2. REFORMING – Reforming is the process which transforms the methane (CH4) and the steam (H2O) to intermediate reactants of hydrogen (H2), carbon dioxide (CO2), carbon monoxide (CO). Carbon dioxide is also added to the feed gas stream at this stage to produce a mixture of components in the ideal ratio to efficiently produce methanol. This process is carried out in a Reformer furnace which is heated by burning natural gas as fuel.
    3. METHANOL SYNTHESIS – After removing excess heat from the “reformed gas” it is compressed before being sent to the methanol production stage in the synthesis reactor. Here the reactants are converted to methanol and separated out as as crude product with a composition of methanol (68%) and water (31%). The crude methanol formed is condensed and sent to the methanol purification step which is the final step in the process.
    4. METHANOL PURIFICATION – The 68% methanol solution is purified in two distinct steps in distillation columns to yield a refined product with a purity of 99% methanol.


    Methanol Holdings (Trinidad) Limited, Trinidad, West Indies
    CMAI forecasts flooded methanol market, Oil&Gas Journal e-newsletter, November, 2005
    Yogi and Gasoline, Peter J. Vanderzee, Energy Security, March 28, 2005
    Methanol, John Zumerchik, Macmillan Encyclopedia of Energy, 2001
    Research in alcohol Fueled-Engines at EPA NVFEL , Matthew Brusstar, U.S. EPA National Vehicle and Fuel Emissions Laboratory February 25, 2003
    Commercial-Scale Demonstration of the Liquid Phase Methanol (LPMEOH tm) Process, Air Product Liquid Phase Conversion Company, June 2004
    “Technical and Commercial Feasibility Study of Black Liquor Gasification with Methanol/DME Production as Motor Fuel for Automotive Uses – BLGMF” , ALTENER, European Union, December 2003
    “Gauging Efficiency from Well to Wheel”, Frank Kreith and R.E. West, Mechanical Engineering 2003

  17. Robert,
    I would break down the discussion of “Feedstock” into three categories: food biomass, non-food biomass and waste. This would allow you to point out how the US approach (trying to convert excess food to fuel) is really limited by available feedstock. It is also easily hijacked by special interests and bogged down by the special priviledges that these special interests have grown accustomed to. You can go on to point out the pointlessness of converting high value calories (food) into (a small amount) of low value calories (fuel). There are, of course, no shortage of example technologies.

    At the opposite end of the spectrum is waste. We don’t have to consider raw material or production costs for waste, since it is a by-product of our other products/activities. You can point out that this is a win-win process, where something that is basically going to take up landfill space is converted to someting useful (fuel) and can be used to replace virgin crude. Most of the time the product is carbon neutral as well. You can mention TDP as an example of this, and be the first writer to properly describe the limitations of the technology.

    You could go on to point out that as fuel gets more expensive, people will conserve more and ultimately produce less waste. While the lower consumption would improve the available waste BTU to required fuel BTU ratio, we will most likely never get to the point where all our fuel needs can be met by waste. Hence non-food biomass will eventually need to fill the gap. You may point out that ideally these crops would need to be cultivated without affecting the production of food crops. You can discuss the various algal production processes, including those that would scrub CO2, NOx and other nasties from flue gas. You can also mention CHOREN technology.

    This goes above and beyond (as many of the suggestions above) but you may continue by describing how much energy people use and how much area would be required to collect that much energy from the sun, etc.

    Man, I get disheartened just listing all the topics! Good luck with this. Let us know when the book hits the selves…

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