Advances in Hemp Biofuel Technology

posted by on November 8th 2012


Seeds destined for oil, which will then be turned into biodiesel (© Jason Rogers)

Exciting new discoveries are emerging regarding the efficiency of hemp biomass when used as feedstock for biofuel production. Biofuels are currently a hotly contested topic, with the United Nations food agency calling on the USA to suspend its biofuel production quota in the light of recent corn crop failures.

In July 2012, corn prices were pushed up by  24.6%, as widespread droughts and heatwaves destroyed crops over vast swathes of rural America, which supplies much of the world’s total stock. Prices have remained high until now, although there was a slight drop in September. The introduction of U.S.  biofuel quotas in 2005 has led to the diversion of food corn to fulfill the mandated quantities, compounding the price rise problem. It is thought that up to 40% of U.S. corn stock is currently being used for biodiesel purposes, although the availability of corn ethanol has decreased and prices have risen sharply here too, prompting many to seek alternative fuels Despite years of research into GM corn strains engineered for drought-tolerance, which have almost certainly lessened the impact of drought on yields, farmers are in crisis and many are struggling to survive.

The viability of hemp as biofuel

The biodiesel potential of hemp as an alternative feedstock is great, not least because many strains are naturally highly resistant to drought without the need for genetic modification. In states such as Iowa, which has been massively affected by crop failures, naturalized ‘ditchweed’ varieties continue to thrive, and were it legal for farmers there to produce hemp, many would already be doing so. The same can be said for farmers throughout America. Several states have even attempted to assemble a state apparatus to issue licenses for hemp cultivation, despite federal restrictions. Hemp also flourishes in less fertile ground than is required for many crops. It can be grown on secondary farmland, possibly even negating the need for a  fallow year in certain crop-rotation systems. In areas where hemp is already cultivated for fiber, the oil-rich seeds are often discarded. They could be used to create biofuel, with no associated increase in emissions or other environmentally damaging effects.   The oil extracted from hempseeds converts to biodiesel (through a process known as transesterification) with an  efficiency of 97%, comparable to other high-performing seed oils, and the resultant biodiesel is effective at lower temperatures than many other biofuels. It also has a low cloud point and kinematic viscosity, meaning that it flows well at cool temperatures and is therefore suitable as a fuel for vehicles. High kinematic viscosity fuels, such as neat vegetable oils, are unsuitable for this purpose due to the possibility of operational problems and deposits left in the engine. For seed crops, the yield per hectare can be as high as 1000 kg/Ha, similar to rape seed. Furthermore, the cellulose within the stalks (up to 77%, depending on the variety) can be fermented to provide ethanol or methanol, both important biofuels, with an efficiency of  around 74%. Yields of above-ground dry matter per hectare can be as high as  25 metric tons; however, the average is around 9 tons. This is comparable to corn, which in the USA averages at around 10 MT/Ha, although the global average is less than half of that.

New developments in biofuel research

A relatively new process known as pyrolysis (thermal degradation in the absence of molecular oxygen) has yielded some very promising  results. Pyrolysis involves subjecting fibrous cellulose-containing plant matter (technically known as lignocellulosic biomass) to intense heat in order to obtain fuel-grade oils.  The same procedure can be applied to raw or lightly-treated hemp biomass. This method has great potential, due to the economic feasibility of using purely waste biomass to produce high quality fuels with little to no impact on food crops, or indeed any other agricultural industry. Along with pyrolysis, a variety of new  biomass treatments are in development, and the range of chemicals that can be sustainably produced is increasing with every new discovery.

A global backlash against biofuels

Testing Biodiesel fuel efficiency (© Official U.S. Navy Imagery)

Elsewhere in the world, arguments against bio fuels have become increasingly strident, with opponents citing potentially greater carbon emissions from palm and rape oil crops (although much of this total is derived from the calculated indirect costs of deforestation), as well as the possible impact on global food prices as edible produce is diverted to the fuel industry. The EU climate commissioner, Connie Hedegaard, recently proposed reducing the target for renewable transport fuels by 2020 from 10% to 5%, just fractionally above the current output of 4.5%, and France has already confirmed a  cap of 7%. This follows years of protests by environmentalists that biofuels would potentially do more harm than good. Although there has been much backlash from the biofuel industry itself as they foresee job losses in the near future, the proposal does not seek to reduce current output, merely to freeze it, so it is unlikely that the industry will suffer greatly.  Despite the increasing backlash against biofuels, which recently led to the U.S. Military issuing statements banning their implementation, the fundamental concept of utilizing biomass for fuel is sound. Continued reliance on fossil fuels is becoming an ever more tenuous position, a fact that is increasingly apparent to energy companies and governments alike. Nevertheless, it is vital that legislation takes into account the suitability of the chosen feedstock, as well as the social and environmental impact of setting aside valuable cropland to produce biofuels. It is clear that palm, rape and corn crops are inherently unsustainable as feedstock choices. The sensible option would be to concentrate global efforts in the direction of crops that do not compete for primary farmland, and those that are not so crucial to food markets that their diversion could cause instability.

Seshata is a freelance cannabis writer currently based in Amsterdam, Netherlands
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