Next Generation Energy is managed and written entirely by Seed editors and expert guest bloggers. Read more about them Intensive technological development is required in order to sufficiently exploit any of the various sources of next generation energy discussed within this blog: wind, solar, agriculture, and ocean currents. The same is true for the use of batteries as a route to store energy for transportation, a necessity if we are to avoid using liquid fuels. Some sources or "wedges" are certainly more nascent than others. I share in the optimism that we can replace current energy sources with more "green" sources and this requires a faith in scientists and engineers to make adequate progress to make next generation energy a reality. We also rely on public and private research and infrastructure investment. The use and promise of plant derived biofuels or agroenergy has been much maligned and with good reason. After all, we are talking about using water and arable land and the inputs that go along with cultivating plants for energy. A great many acres in the world are farmed in a rather unsustainable manner and why should we expect energy crops to be any different? To grow our food, we often add excessive amounts of fossil fuel derived fertilizer to the land and subsequently the water table and add heaps of carbon to the atmosphere evolved from the soil and by powering farm equipment. Few of us don't support this industry through our consumerism. Methods to restore fertility to farmland are no mystery. We must implement these practices which include cultivating prairie grass mixtures that serve as a biofuel feedstock.
Miscanthus at maximum biomass topping 11 feet, shown
with Emily Doherty for contrast.Photo Illustration
courtesy S. Long Lab, University of Illinois, 2006
Some have suggested we abandon the practice and prospect of agroenergy due to the risks of a net negative effect on our atmosphere, land, and water quality. A free market system without regulations and with or without subsidies can easily encourage deforestation and excessive chemical inputs and irrigation to produce biomass for energy - this is predictable human behavior and obviously not the sustainable system we envision. However, this behavior is not necessary. I suggest we invest in developing more sustainable agricultural practices for the production of both food and energy. In addition to science and technology, we need to develop our society and civilization to implement solutions to our current energy crisis. Biofuel crops have tremendous potential to be part of the solution.
It is safe to say that there is a consensus among scientists, business, and even politicians, that corn starch and sugarcane based ethanol production is neither sustainable nor scalable. It seems unnecessary to reiterate, but the future of plant-derived energy is not based on corn and sugarcane. The goal is to use the entire plant which is mostly cellulose, hemicellulose, and lignin, not just the grain or phloem sap. Collectively this material is referred to as lignocellulosic biomass. It can be deconstructed to simple sugars or burned for several purposes outside the scope of this post. While some species are cultivated as forage and feed and trees for paper pulp, we do not have a suite of domesticated species to meet our needs for biofuel feedstocks. Plant biologists are therefore presented with a fascinating challenge; by plant breeding and biotechnology, develop energy crops and best practices for their cultivation. First we ask the question, what do we wish for in an energy crop?
High yield. This goes without saying and is really a culmination of various attributes leading to a complex and compound trait. We need a dramatically positive energy balance along with maximum output per unit area.
Efficient solar capture. Plants can fix carbon different ways and while the three forms are adaptive to different environments, C4 is generally considered the most efficient. C4 plants include the tropical grasses maize, sugarcane, millets, and Miscanthus. Switchgrass is a C3 plant and is thus potentially more adapted to cooler conditions than C4 plants.
Water use efficiency. Water is definitely a limiting factor and our crops should use as little water as possible in an efficient manner.
Nutrient use efficiency. Fertilizer production requires energy and one ingredient is fossil fuel. Exogenously applied fertilizer often ends up in the water table as a pollutant. Thus, atmospheric carbon and water quality are influenced by nutrient use efficiency.
Pest resistance. Beyond potential toxicity, application of fertilizers and pesticides requires the use of farm equipment and thus fossil fuels. Low pest load can translate to higher yield and quality of biomass and a better energy balance.
Perennial growth habit. Plants that last through many years, rather than an annual growth habit tend to develop a more complete and long lasting canopy, thus out competing weeds as well as conducting photosynthesis for a relatively extended period of time.
Nutrient cycling. Steve Long at the University of Illinois found that at the end of the growing season, the energy crop Miscanthus transported nitrogen from the above ground biomass to the root system, thus preserving these nutrients rather than losing them during biomass processing. I might add, there are several obvious avenues that have been developed to study related mechanisms in plants that could easily be applied (if adequately supported) to explore this mechanism.
Amenable to existing farm equipment. Adaptation of energy crops by farmers will certainly be less problematic if they can be planted and harvested with existing machinery. Also, the ability to harvest the crop quickly and at different times of the year will aide in meeting a persistent need for feedstocks from a seasonal source.
Non-invasive. Some species akin to an ideal energy crop are considered to be invasive species. That is to say they have the potential to heavily colonize a particular habitat regardless of being indigenous or not. The impact of anyone species can and should be tested in various environments. This process should come with clear guidelines and ought to be easily executed. Another form of invasiveness is through cross-pollination. Biotechnology will not be ignored as an option for energy crop improvement (an excellent subject for a future post). The risk of transgene escape must be assessed prior to cultivation, as it is with food crops.
End use quality. Of course, the species must exhibit a high conversion efficiency, meaning it is easy to deconstruct and/or convert into energy, be it direct combustion or deconstruction to simple sugars for subsequent conversion to high energy particles.
What to do? Without dismissing several other interesting and viable options including sorghum and mixtures of highly diverse species, many non-food perennial grasses potentially fit the bill and could be subject to rapid (5 to 20 years) development as biofuel feedstocks. Several species under consideration and development include switchgrass, Miscanthus, Reed Canarygrass, and Cordgrass. There very well could be a gigantic leap in yield for energy crops in the near future or at least on the time scale of crop improvement, which is one or two decades. To facilitate the development of suitable energy crops and agronomic practices, more basic and applied research is called for. Many of the properties discussed above are similarly important to food crops; thus, amplified effort in energy crop research should not be seen as a tradeoff. On the contrary, it will add to the plant science knowledge base. We should move forward with care and optimism to explore further development of an agroenergy industry, keeping in mind what we know about the past performance of the biofuel industry and the potential pitfalls.
Reference
Heaton E.A., Long SP, Voigt TB, Jones MB, Clifton-Brown J (2004) Miscanthus for renewable energy generation: European Union experience and projections for Illinois. Mitigation and Adaptation Strategies for Global Changes. 9:433-451
Comments
One very naive question to either smack down or encourage a certain segment of my readership-- are any of the Cannabis species in/consistent with your rules of thumb?
Posted by: DrugMonkey | July 20, 2008 10:32 AM
Prof Hazen, as one who is getting more interested in plant biotechnology and biofuels, I really enjoyed this detailed and scholarly post.
I appreciate your point that transgenic plants should not be invasive but how do colleagues in your field feel about kudzu (Pueraria lobata) as a biomass source? As I'm sure you know, it is rampant across the southeastern US and is also a nitrogen fixer with plenty of starches, especially in the roots. But although we see it all over the place, I wonder if it really produces as much biomass per unit area as Miscanthus and switchgrass.
In addition, would you care to comment on the magnitude of energy inputs required to manufacture the scale of recombinant enzymes needed for lignocellulosic hydrolysis into fermentables?
Posted by: Abel Pharmboy | July 20, 2008 1:05 PM
NONONO!!!!
Doesn't anyone here realize how difficult it is to break lignocellulosics down to sugar? This is not some easy disassociation reaction. It takes brutal treatment with acid or alkali (read 20% NaOH on wood, at 150-200C, for 2-4 hours), and the lignin gets in the way at every step. There's 150 years of wood pulping and cellulosic plastics literature that will instruct one on how difficult a course this is. And once you break it to sugar you're at the starting point for a fermentation and distillery, which by themselves make this a non-starter.
Be wary of scientists from major universities telling you this will be child's play. They only want the money, and will explain why it didn't work once the money's spent.
Regarding cannabis, the close relative kenaf has been extensively studied (kenaf leaves are a match in appearance). A subcontinent plant used as a secondary source for rope-making fiber, it can be grown for enormous yield. IF: you don't mind loading the soil with root nematodes AND you fertilize the heck out of it AND you irrigate it like crazy. I visited a neglected demo plantation in south Texas about 15 years ago. If you do not farm it intensively it grows into shrubby bushes and not into the 10-15 foot stalks you see in the promotional literature.
Posted by: tom quick | July 21, 2008 9:55 AM
Good question Drug Monkey and I suspect some of your readers know more about this than I do, but the answer is yes, the species does exhibit many desirable energy crop properties and I would be interested to see how cannabis would perform in field trials. However, unlike funds available in the US to study cannabis as a drug, I'm not aware of any to study cannabis as a crop. I don't expect to see much happen in this area anytime soon. While the THC content is somewhat unique many other species can serve as an energy crop.
The kudzu story is an interesting one. It is indeed the scourge of southeast woodlands and if it were extracted from those lands then it may serve as a useful feedstock. However, as I crop I expect it might have limited use. Digging up roots for starch is definitely not part of the equation as far as an ideal energy crop goes. Such a practice is cumbersome and costly compared to harvesting the above ground biomass leaving behind healthy soil and sequestered carbon. Also, cultivating kudzu may be problematic considering its indeterminate vine nature and lets not forget the invasive issue.
I'm not aware of the energy cost to produce recombinant enzymes needed to convert plant cell walls to biofuel. Great question though. One issue is that the process is not fully developed, or certainly not the numerous ways likely to take shape and be tested in the near future. At best the industry is in the pilot phase moving towards demonstration plants in some cases.
Posted by: Sam Hazen | July 21, 2008 4:04 PM
I'm not aware of the energy cost to produce recombinant enzymes needed to convert plant cell walls to biofuel. Great question though. One issue is that the process is not fully developed ...
Which is a major problem. According to Congressional mandate (the 25 x 25 issue), cellulosic ethanol is due to come online by 2011.
Rather, we should rely on thermochemical processes which are already available.
Posted by: TomJoe | July 21, 2008 4:59 PM
While all the discussion of cellulostic ethanol is certainly interesting... we seem to be missing something major.
What other alternatives do we have for transportation fuel?
Off the top of my head, all I can think of are: petrol (gasoline), petro-diesel, CNG or LNG, ethanol, and biodiesel.
Of course we should count in increased efficiency and electricity as good alternatives, but these are 'partial substitutes' in that they can only displace some of the demand. Mind you, that does not mean we shouldn't pursue them in a big way... all the info I have indicates that they are by far the most cost effective and readily available options we have. However, that good step will only get us part way towards the eventual goal of sustainability and carbon neutrality.
I would very much appreciate someone doing a top level post reviewing the pros and cons, cost analysis, and near-term technological prospects for all the transportation fuel options.
Posted by: travc | July 21, 2008 7:53 PM
Why are the readers or authors of this blog so quick to completely miss an extremely OBVIOUS fact. THC is a hydrocarbon and is an oily substance, however it is also sticky and not very liquid. Being a hydrocarbon it seems like it could easily be converted into some sort of liquid biodiesel and it also seems cannabis is the only plant to be completely covered in oily hydrocarbons.
Also someone above mentioned kenaf. I have feeling that person completely missed the point of mentioning cannabis, kenaf is most similar to cannabis in its fiber content (similar to hemp) however it does not have the same outward hydrocarbon content.
Furthermore, THC production cannabis plants are completely different from those used for hemp. As one produce drugs and the other uses fibers. I do not think the point was to grow hemp and turn the fibers into ethanol, but the advantage of cannabis crops is the production of a hydrocarbon. However, cannabis plants do have one of the highest cellulosic contents of any plant and therefore when cellulosic ethanol production becomes economical all the extra plant waste could be turned into ethanol and combined with the biodiesel prior to that plant waste can be used for paper, clothing, plastics, or returned to the soil to maintain soil quality.
I don't know how easy it would be to turn THC into a hydrocarbon fuel or how economical its production would be or could be (as potency increases over time), but I also know we will never know until the drug war ends and the drug war has impeded much psychological science and studies of effects on drugs on the brain due to the difficulty of getting the required permits to possess and use drugs from DEA for research purposes and it has also held back much science studying plants and various other organisms that contain drug products. Personally as a science nerd this is one of the greatest tragedies of the drug war in addition to the millions needlessly imprisoned is that not only has it hurt so many people but it is contributing to ignorance and blocking scientific progress. Reminds me of a past time when scientists were demonized for determining that the earth was round or wasn't the center of the universe. Likewise, any who wants to due research on drugs or natural organisms that produce drugs or drugs precursors is kept out of the field if they are doing any research other than trying to prove that they are bad and should be kept illegal. Science shouldn't have an agenda. End the drug war not just for freedom from police intervention, not just the freedom to choose how people modify their mind, but also for intellectual and scientific freedom. And maybe for fun too :)
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Posted by: fx15 zayıflama | July 22, 2008 3:18 AM
re: kudzu, I think all those south easter US types are just hoping someone will find a way to make it pay to rip out all those invasive vines...
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Posted by: chat | January 27, 2009 4:11 PM
Throw off your sins or face God for assuming his role in nature.
Posted by: The Pope | February 5, 2009 9:56 PM
Here some more for you...yeah, yeah, I know... If you have a personnel thing against cannabis, or you are like "well that is just illegal and yeah". just save your typing, because you have no idea the harm you are promoting or support of, the Illegality of the Status Quo.
Approximately 6% of the agricultural land area of the contiguous United States would produce more Cannabis Biomass than is required to supply all current demand for gasoline, diesel, and oil.
The Cannabis Biomass Energy Equation (CBEE), given practical application in the Cannabis Biomass Resource and Pyrolysis Functions (CBRPF), explains and establishes, for the first time on record, how Cannabis, uniquely among plant species, produces fuel-energy cheaper per BTU than fossil fuels and uranium, and is capable of their economic replacement. Profound amelioration is made available to the world and its peoples from these facts, which are expounded in-depth. Chemistry: shows Cannabis-Methanol fuel-energy pollution-free, which will have stabilizing result on Global Warming.
When cannabis is cultivated for its profitable nutritious seed-food (which, as noted, does not contain relaxant ingredients), all the by-products (which are source to literally thousands of commerical products), are derived from a resource which is thus production-cost-free (i.e. free). This is possible, because of the many application of the same plant grown for multiple uses at the same time. Making an unbelievably low cost production.
To recapitulate, the free fibres and free cellulose-rich wood-hurd bulk residues, flowertops and foliage, yield economical (cheap) cannabis products which include the illimitable fuel and energy, all types of plastic products, fine-grade yarn and Dresden Cotton ®, textiles, paper, cardboard, newsprint, man-made fibres (by cellulosic polymerisation, e.g. nylon), medication, lightweight building materials (Isochanvre ®) etc.
The U.S. National "Soil Bank’s" registered fallow land (circa 89 million acres) can be planted with soil-enriching, non-depletive cannabis as a fallow rotation crop, producing enough Cannabis-Methanol, oil, lubricants and BTU-gas for all North American land, sea and air transportation requirements.
The CBEE will do far more, please just find a copy of the book 'Cannabis: The Facts, Human Rights And The Law' or visit my website ( that has a small section on this, and soon a whole section dedicated to the CBEE.
See: THE REPORT: Cannabis: The Facts, Human Rights And The Law
Supported by an Adviser to U.S. government Nobel laureate professor emeritus.
Endorsed by a Professor of Physiology Fellow of the (U.K.) Royal Society.
Endorsed by eminent authors, academics, doctors and judges (U.S. and U.K.).
Posted by: Dan | April 16, 2009 5:50 PM
The CBEE will do far more, please just find a copy of the book 'Cannabis: The Facts, Human Rights And The Law' or visit my website ( http://suitsusall.org/report.aspx ) that has a small section on this, and soon a whole section dedicated to the CBEE.
Posted by: Dan | April 16, 2009 5:53 PM
I would very much appreciate someone doing a top level post reviewing the pros and cons, cost analysis, and near-term technological prospects for all the transportation fuel options.
Posted by: diyet | June 8, 2009 5:44 PM
Dan ive already read that it makes sense but the question always is..... how can you prove it? nobody is allowed to grow cannabis, unless you own a hemp farm i suppose.
It is a very well written arguement and the point is, what can go wrong? it's not like it's not already easier for high schoolers to get weed than beer.... But willful ignorance will probably rule the day.
Posted by: Carlos | August 10, 2009 6:24 PM