Several recent studies about the carbon balance of first-generation biofuels, including two analyses published in Science, are based on assessments of current land use practises. These studies are important, but the conclusions drawn from them are often seriously flawed. Moreover, if these conclusions are placed in a neo-malthusian perspective on population and natural resources, they cannot be taken seriously at all because there is no credible basis for neo-malthusianism in the first place.
Let us first note that only a fraction of the current biofuels are produced from crops grown on cleared high carbon land like forests. The vast majority is based on low carbon land, so we are only looking at exceptions here. Scientists analysing the long term potential of explicitly sustainable biofuels have clearly outlined how much low carbon land is available on a global scale, and it is estimated to be more than 1 billion hectares - that is: non-forest land available after all food, fiber and feed needs for growing populations have been met (more here). In short, technically speaking, the planet can relatively easily sustain the production of both food and fuels for a growing population, sustainably.
That said, let's look at the current land use practises analysed in the studies. These practises involve the conversion of 'pristine' systems like forests, woodlands or grasslands, to make way for monocultures of energy crops . Under these practises, the biomass that is cleared is often burned, resulting in large carbon emissions. Biofuels made from low yielding crops grown on this land thus have a large 'carbon debt'. It can take years or decades before biofuels have repaid their debt and begin to reduce emissions (by replacing fossil fuels).
But all these analyses are based on existing, primitive land use practises and on first-generation, inefficient biofuels made from crops like corn or soybeans. They do not take into account new energy crops (e.g. crops that yield far more biomass and are engineered to store far more CO2 than ordinary crops), the use of plantation residues, new bioconversion technologies, and the radical option of capturing and storing carbon from bioenergy production.
Those who use current studies about the carbon balance of today's incredibly inefficient biofuels to conclude that all biofuels are incapable of reducing emissions are making a grave mistake. In fact, new and future land use practises by themselves change the picture entirely, and make biofuels and bioenergy the most radical tool in the fight against climate change. Add new crops and new conversion techniques, and it will be clear that biofuels present major benefits.
New land use practises
Let's explore these new concepts - they are based on developments that are already taking place. The schematic above outlines them in brief.
First of all, a major leap forward towards making biofuels carbon neutral from the very start - cancelling the carbon debt at once - is very simple. It consists of using the original biomass (e.g. woodland or forest) as a bioenergy feedstock. When clearing a forest, it is foolish to burn the wood which is the current practise, because this biomass is itself a highly valuable energy source. Instead of wasting the energy by burning the wood, it will be used as a biofuel feedstock.
Decentralised biofuel production plants that can be located close to the land to be cleared are already here. These plants draw on a process called fast-pyrolysis. It transforms any type of biomass into bio-oil, which can be further upgraded into transport fuels or used in power plants.
Using the biomass of the land clearance as a biofuel feedstock immediately pays back the bulk of the carbon debt that would have resulted from burning this biomass without using the energy contained in it. The only carbon debt left is that resulting from changes in the below-ground biomass, but in most cases this can be offset quite quickly (e.g. when a perennial grassland is replaced by polycultures of perennial energy grasses). Of course, this new land use technique requires the creation of infrastructures (such as roads), but these are likely to benefit local communities greatly.
Virtually no study looks at this simple step. It is however already being implemented. An example comes from old palm oil plantations that are being replaced by new ones. The old biomass stock - entire trees - is being converted into biofuels that replace fossil fuels. A Canadian bioenergy company (Buchanan Renewable Energies) is doing this in Liberia, where it is paying to use old palm forests' biomass as a feedstock for the production of pyrolysis oil. After this first transformation, the cleared land will be used for a new plantation. Fuels from this new plantation have no 'carbon debt'. This concept can (and should) be applied to all new biofuel ventures that convert undisturbed grasslands, wood lands or forests into energy crop plantations.
This new land use practise is however only a first step towards far more interesting bioenergy concepts. In the future, original biomass will not only be converted into bioenergy or biofuels, but the fuel production process itself will be coupled to carbon sequestration techniques. These come in two forms: either geosequestration (storing CO2 in geological formations) or biochar systems (storing carbon in soils via charcoal or pyrolysis char).
The process works as follows: original biomass (e.g. a woodland) is used for the production of a biofuel such as pyrolysis oil. The local plant may itself already capture and store its own CO2 emissions (a first example of CCS coupled to biofuel production comes from the U.S. where the Midwest Geological Sequestration Consortium recently received $66 million to sequester CO2 from a biofuel plant - more here). The fuel is then sent to a facility where it is used for the production of either electricity and heat, a fully decarbonized biofuel (such as biohydrogen) or a low-carbon biofuel. At this facility, the CO2 is again captured and stored, before the decarbonized form of energy is used by the consumer. The end result is carbon-negative energy that yields negative emissions:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: land use :: emissions :: carbon capture and storage :: efficiency ::
Such carbon-negative fuels and energy is a radical tool in the climate fight. Unlike any other type of renewable energy, it actually removes CO2 from the past from the atmosphere.
Scientists working for the Abrupt Climate Change Strategy group, a think tank with a mandate from the G8 to study options for us to survive abrupt climatic change, calculated that if such systems were implemented on a global scale, we can bring atmospheric CO2 levels back to pre-industrial levels by mid-century (more here).
Besides the option of capturing and storing CO2 from bioenergy and biofuels, a whole series of new developments in all biofuel production steps have to be taken into account.
New crops, new bioconversion techniques
New land use practises were already discussed. Now let's look at developments in the field of energy crops, bioconversion, agronomy and the use of residues. Current biofuel crops like corn or soybeans are truly inefficient because biofuels made from them only utilize a fraction of the biomass grown, that is, easily extractible starch or oil. These first-generation biofuels have no future and are no longer of interest to the bioenergy community.
A large number of plant biologists and bio-engineers has already developed new crops that either yield far more biomass (which immediately clears much of the carbon debt), or that store far more CO2 than ordinary crops, or that contain in them codes for easy bioconversion. We will limit the discussion to a few examples of such crops: high-biomass sorghum (more here), eucalyptus trees with higher carbon storage capacity (here, and another similar crop - a hybrid larch with enhanced CO2 sequestering capacity, here), maize that contains its own bioconversion enzymes (previous post) and low lignin sorghums that can be turned much easier into fuels (here).
Secondly, an enormous number of efficiency leaps in biofuel production processes has emerged over the past years. This process is ongoing. Almost every day Biopact reports about them. Yesterday, scientists reported they have developed a new nano-engineered molecular sieve that dehydrates biofuels much more efficiently - which means less energy is needed, thus lowering the emissions from the production process (more here). Also yesterday, ZeaChem announced it succeeded in improving ethanol yields from wood via a hybrid conversion process based on thermochemical and biochemical transformation into hydrogen (used to power the process) and acetic acid, which is consequently turned into liquid fuel in a highly efficient manner. The yield increase: 50% (earlier post).
This type of evolutions occurs virtually every day and is tilting biofuel production to ever higher efficiency and lower emissions. Sadly, it takes a while before environmentalists, conservationists or researchers become aware of them and take them up in their analyses.
Third, mere agronomic interventions succeed in improving the carbon and energy balance of biofuels. One of the studies recently published in Science gives the example of growing polycultures of native prairie grasses - these polycultures actually store large amounts of carbon in soils, and by themselves become a strong carbon sink. Using the grasses as a bioenergy feedstock results in carbon negative fuels, merely as a result of good agronomic practises and because of the nature of these grasses (previous post). The original researcher who conducted this line of studies, David Tilman, was a co-author of one of the Science papers published today.
Finally, an area in which huge potential can be found is in the utilization of plantation and processing residues from existing agricultural operations and biofuel operations. Recently, we referred to the potential for the production of biohydrogen from palm oil residues. A palm plantation yields farm more biomass than is currently used in the form of oil. If these vast amounts of residues are used productively instead of burned or dumped as waste, the carbon balance of biofuels from the oil is seriously improved (previous post). There is similar potential is virtually all agricultural operations today. The same process can be applied in biofuel operations, where residues and byproducts (such as glycerine in biodiesel) is used as a feedstock for a myriad of green products that replace oil, coal and gas.
In short, we agree with the growing body of researchers who point to the many potential drawbacks of primitive, first-generation biofuels. Biopact has long ago distanced itself from these fuels (an exeption would be fuels like current sugarcane based ethanol in Brazil). We think much more care must be taken to assess the full lifecycle carbon emissions from biofuels, as well as indirect emissions that occur elsewhere on the planet because of the massive use of particular crops in one place (e.g. corn in the U.S. driving the expansion of soy in the Amazon).
But all this should not negate the fact that there is a range of bioenergy and biofuel production concepts that offers major benefits. Neither should the studies based on current inefficient biofuels halt the exploration and development of new crops and bioconversion technologies. The challenges presented by climate change and growing energy insecurity are too important and require continued investments in new technologies.
Scientific literature on negative emissions from biomass:
H. Audus and P. Freund, "Climate Change Mitigation by Biomass Gasificiation Combined with CO2 Capture and Storage", IEA Greenhouse Gas R&D Programme.
James S. Rhodesa and David W. Keithb, "Engineering economic analysis of biomass IGCC with carbon capture and storage", Biomass and Bioenergy, Volume 29, Issue 6, December 2005, Pages 440-450.
Noim Uddin and Leonardo Barreto, "Biomass-fired cogeneration systems with CO2 capture and storage", Renewable Energy, Volume 32, Issue 6, May 2007, Pages 1006-1019, doi:10.1016/j.renene.2006.04.009
Christian Azar, Kristian Lindgren, Eric Larson and Kenneth Möllersten, "Carbon Capture and Storage From Fossil Fuels and Biomass – Costs and Potential Role in Stabilizing the Atmosphere", Climatic Change, Volume 74, Numbers 1-3 / January, 2006, DOI 10.1007/s10584-005-3484-7
Further reading on negative emissions bioenergy and biofuels:
Peter Read and Jonathan Lermit, "Bio-Energy with Carbon Storage (BECS): a Sequential Decision Approach to the threat of Abrupt Climate Change", Energy, Volume 30, Issue 14, November 2005, Pages 2654-2671.
Stefan Grönkvist, Kenneth Möllersten, Kim Pingoud, "Equal Opportunity for Biomass in Greenhouse Gas Accounting of CO2 Capture and Storage: A Step Towards More Cost-Effective Climate Change Mitigation Regimes", Mitigation and Adaptation Strategies for Global Change, Volume 11, Numbers 5-6 / September, 2006, DOI 10.1007/s11027-006-9034-9
Biopact: Commission supports carbon capture & storage - negative emissions from bioenergy on the horizon - January 23, 2008
Biopact: The strange world of carbon-negative bioenergy: the more you drive your car, the more you tackle climate change - October 29, 2007
Biopact: "A closer look at the revolutionary coal+biomass-to-liquids with carbon storage project" - September 13, 2007
Biopact: New plastic-based, nano-engineered CO2 capturing membrane developed - September 19, 2007
Biopact: Plastic membrane to bring down cost of carbon capture - August 15, 2007
Biopact: Pre-combustion CO2 capture from biogas - the way forward? - March 31, 2007
Biopact: Towards carbon-negative biofuels: US DOE awards $66.7 million for large-scale CO2 capture and storage from ethanol plant - December 19, 2007
Biopact: Biochar and carbon-negative bioenergy: boosts crop yields, fights climate change and reduces deforestation - January 28, 2008
References to new crops, bioconversion methods and agronomic advancements can be found throughout Biopact's archive. References mentioned in this article are:
Biopact: Scientists develop low-lignin eucalyptus trees that store more CO2, provide more cellulose for biofuels - September 17, 2007
Biopact: Japanese scientists develop hybrid larch trees with 30% greater carbon sink capacity - October 03, 2007
Biopact: Third generation biofuels: scientists patent corn variety with embedded cellulase enzymes - May 05, 2007
Biopact: Carbon negative biofuels: from monocultures to polycultures - December 08, 2006
Biopact: Tallgrass Prairie Center to implement Tilman's mixed grass findings - September 02, 2007
Biopact: Sun Grant Initiative funds 17 bioenergy research projects - [on high-biomass sorghum] August 20, 2007
Biopact: Ceres and TAES team up to develop high-biomass sorghum for next-generation biofuels - October 01, 2007
Biopact: Scientists release new low-lignin sorghums: ideal for biofuel and feed - September 10, 2007
Biopact: Major breakthrough: researchers engineer sorghum that beats aluminum toxicity - August 27, 2007
Biopact: U.S. scientists develop drought tolerant sorghum for biofuels - May 21, 2007
Biopact: Sweet super sorghum - yield data for the ICRISAT hybrid - February 21, 2007
Biopact: Mapping sorghum's genome to create robust biomass crops - June 24, 2007