From Robert Rapier at R-Squared:
As explained in the previous essay, my new role involves development of an integrated bioenergy platform. We believe this to be a different way of looking at the problem of turning biomass into energy, and then ultimately supplying that energy to customers. We are not tying ourselves to a specific technology platform; we are using different platforms as suited for specific local needs. We are also as concerned about the sustainability of the biomass as we are the sustainability of the processes we will utilize.
This is a key point—the technology and the approach depend widely on a long list of local parameters. Creating a platform that can adapt to local conditions is the future of biofuels and energy. All the focus to date has been on crops, but more and more people are talking about mass—and therefore trees—as part of the solution.
So why do we like woody biomass? Why not switchgrass? Sugarcane? Crop residues? Various sources of biomass have their strengths and weaknesses. Very high on the list for a sustainable model is to take care of the soil. One of the questions I sometimes pose is “What would the soil condition be after 500 years in a particular service?” If the answer is not approximately as good or better than the present, then it doesn’t meet the sort of criteria that I am looking for (of course taking into consideration that the soil doesn’t have to be utilized for the same purpose for the entire duration).
Trees are different. During the first 10 years or so of their lives, trees can accumulate biomass at the rate of 7-10 bone dry tons per acre per year. You may see some switchgrass yields that are claimed to be that high, but those were almost certainly with fertilizer and plenty of water. But even if the yields were the same, the difference is that you have many harvests of the switchgrass over 10 years to get the same yield as one harvest of trees. Each harvest comes at the cost of energy and labor inputs.
An important point that requires our focus to shift long-term. Rather then harvest annually and manage an annual cashflow, we need to develop projects that are 7 or 10 years out. This kind of thinking helps damper situations like we saw with ethanol.
But there is an even more compelling reason to utilize trees. Unlike most of the short-rotation crops that are frequently discussed as feedstock for fuel production, trees can actually improve the quality and health of the soil.
Depending on the specific trees you use, managed forests can provide fuel while improving soil quality. You could also envision rotating trees with other crops to rebuild fertility.
So do not weep for the trees we will use. The right trees are ideal sources of biomass if they are properly managed. Besides providing fuel, they are going to perform an important function – recycling nutrients from the subsoil to the topsoil. The trees that are cut will be replanted.
Lastly, this can be done in a way that actually upgrades the soil. Something nobody is talking about right now is the value of good compost. Considering that every ton of green material we add to the top of the soil is a ton of carbon, this market is going to be large.
