INSIDER: Responding to Questions about Bioenergy
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WRI released a working paper titled Avoiding Bioenergy Competition for Food Crops and Land in January, articulating reasons the world should avoid dedicating land to bioenergy production if it is to sustainably feed the global population in 2050. The paper explains that the world’s land is under increasing demand to grow food, produce timber, store carbon and protect biodiversity. Dedicating land to bioenergy is highly land-inefficient, and therefore produces energy with high opportunity costs.
Among the comments on this paper was a critique by Michael Wang and Jennifer Dunn of Argonne National Laboratory. In a response, the paper’s lead author shows that key assertions in the Wang and Dunn critique are factually incorrect and other arguments unsupported. Moreover, even if they were correct, nothing in the critique challenges the basic principles that underpin the recommendation against the dedicated use of land for bioenergy.
In brief, the responses include:
The WRI paper’s calculation is accurate that an amount of biomass equal to all of the world’s biomass harvested in 2000 would be needed to produce just 20 percent of global energy in 2050. The Intergovernmental Panel on Climate Change (IPCC) has reported a similar number. Claims otherwise misread a table in the underlying study.
The paper’s analyses account for all byproducts of biofuel production, as explained in the endnotes. When byproducts are used for food or feed, the study’s authors counted them as remaining in the food supply. When byproducts are used for other forms of energy, such as electricity from unconverted cellulose or bagasse, the study’s authors counted them in the net energy calculations.
The paper properly estimates that on about 75 percent of the world’s land, solar photovoltaic cells (PV) would produce at least 100 times more energy than bioenergy per hectare. This calculation compares PV and bioenergy separately on a “cell by cell” basis, dividing the world’s land into 259,200 cells. Put another way, on about three-quarters of the world’s land, the lowest advantage of solar to bioenergy is 100 to 1—the advantages of solar are even greater on nearly all of this land. In the single cell of the world’s land for which bioenergy production is most efficient, solar PV would still generate 40 times more useable energy per hectare.
The paper’s comparisons of cellulosic bioenergy production with solar energy are generous to bioenergy. The paper compares estimates of future bioenergy production that are possible (yet still optimistic and not yet achieved today) against solar PV efficiencies in commercial operation today. Contrary to claims, the paper evaluated a range of bioenergy productivities. Even a yield of 24 dry tons/hectare of biomass on ideal land in the United States would still convert only 0.35 percent of solar radiation into useable energy, and therefore require 30 times more land than PV to produce the same quantity of useable energy.
Claims that abundant “marginal land” exists for bioenergy confuse land that is marginal for cropping with land that is marginal for all purposes. Even if land is marginal for crop production, land with reasonable rainfall and therefore suitable for bioenergy will nearly always be able to support vegetation that provides other valuable benefits, including carbon storage.
Claims that competing for the world’s agricultural land through bioenergy “could” actually boost food availability are based on speculation, and are contrary to both evidence and standard economic principles.
The claim that carbon dioxide emissions from vegetation and soils have less of a greenhouse gas effect than the release of carbon dioxide from fossil fuels is scientifically inaccurate. The mere fact that plants used for energy absorbed carbon when they grew does not make their use carbon-free except to the extent that the use of bioenergy results in additional plant growth than what would otherwise have occurred.
Other more general criticisms do not deal with the fundamental challenges that (a) the world is likely to expand agricultural area even without biofuels; (b) the demand for land for food, timber, carbon storage and biodiversity gives land in general and fertile land in particular high opportunity costs; (c) the inefficiency of bioenergy production per hectare limits that land’s value for energy; and (d) solar provides an alternative means of producing far more energy per hectare, and can use infertile land.
For more information, read the full response to the Wang and Dunn critique and the full working paper.