Cutting down trees to generate biofuels to substitute for fossil fuels can’t make sense in terms of carbon accounting, can it? I never thought so, but apparently some people have contended that it does. This Project Syndicate essay from Bjorn Lomborg addresses the question, and I think it’s worthy of consideration not just because I think his argument is persuasive (which may reflect the quality of the argument or my confirmation bias, take your pick), but also because he provides several links to published papers that suggest that such strategies may actually increase GHG concentrations.
His point is more important and more subtle, though. What happens when deliberate cultivation of biomass crops changes the land use and moves agricultural production to other plots of land?
But the biggest problem is that biomass production simply pushes other agricultural production elsewhere. Studies are just beginning to estimate the impact. In Denmark, a group of researchers estimated by how much various energy crops would reduce CO2 emissions. For example, burning a hectare of harvested willow on a field previously used for barley (the typical marginal crop in Denmark) prevents 30 tons of CO2 annually when replacing coal. This is the amount that proud green-energy producers will showcase when switching to biomass.
But burning the willow releases 22 tons of CO2. Of course, all of that CO2 was soaked up from the atmosphere the year before; but, had we just left the barley where it was, it, too, would have soaked up quite a bit, lowering the reduction relative to coal to 20 tons. And, in a market system, almost all of the barley production simply moves to a previously unfarmed area. Clearing the existing biomass there emits an extra 16 tons of CO2 per year on average (and this is likely an underestimate).
So, instead of saving 30 tons, we save four tons at most. And this is the best-case scenario. Of the 12 production modes analyzed, two would reduce annual CO2 emissions by only two tons, while the other ten actually increase total emissions – up to 14 tons per year.
Rather than displace agricultural production (with all of the attendant distortions in other markets that would arise), I tend to think about doing research in and exploring technologies for biomass waste recycling. Things like anaerobic digesters to process dairy waste and use it to generate electricity. In that case you are generating two benefits — electricity for consumption and waste management — so the combined value of those two benefits may make a more costly technology economical. Here are some suggestive numbers about that net benefit from Wisconsin, although I caution putting too much credence in them.