What’s the best use for our ‘waste’ biomass?

Photosynthesis looks like an elegant answer to the energy problem and the carbon problem at once, because it captures both in the same material, and the annual global flow is enormous. The catch is that nearly all of it returns to the atmosphere within about a decade through decay or burning, so any value lies in intercepting it first. An intercepted ton can have its chemical energy extracted, or its carbon locked away for centuries, and burning it with carbon capture does both. That dual proposition is why economy-wide decarbonization models tend to take as much of it as their assumptions allow, which for Lubershane makes the supply question prior to the choice question.

His answer on supply is: not much, and he narrows the resource twice before comparing any uses. Wild land is out, because intact ecosystems supply pollination, water purification and erosion protection for free only if given space, and he reads several trends as showing they are already at risk; he thinks we probably need to give some appropriated land back. Land farmed or logged is mostly spoken for. He can imagine freeing some of it by eating less meat, but expects the world to demand more animal protein as it grows richer, and expects a warming climate to squeeze yields, so he would rather that land grew food. Planting crops specifically for fuel or removal he says he is not entirely opposed to, but his prior is to be very skeptical, on physical grounds: photosynthesis converts a few percent of the sunlight falling on a field where photovoltaics convert something like a fifth, so anything routed through a plant makes much worse use of land than photovoltaics do. What is left is residues, and they are awkward. They are cellulosic and therefore hard to break down, usually damp, scattered over millions of acres and thousands of facilities, and chemically variable from stream to stream, all of which makes collecting and converting them expensive. Sized against the problem, all of it would cover roughly 5% of American primary energy and, separately, of global emissions. He judges that big enough to be worth the trouble.

Everyone wants it. He walks through power generators repowering coal boilers, gas utilities buying pipeline-ready biomethane, shipping lines after methanol, airlines after jet fuel, ethanol producers, hydrogen projects, low-carbon concrete and bioplastics. The economist’s test is which use earns the most over its cost at a rational, universally applied carbon price, and on his own comparison the winner is pure carbon removal, because it is both valuable and cheap: burying carbon skips the gasification and gas-capture steps that everything else has to pay for. Renewable natural gas is probably the cheapest fuel to make from gasified biomass, but methane is not worth much and is not especially carbon-intensive to begin with, so even a $200 per ton carbon price does not close the gap. Jet fuel is worth far more but costs far more to produce, and also fails at $200, though here he thinks better upgrading technology could cut production cost by more than half. The hydrogen-with-sequestration route that the models favor is both valuable and expensive, and it is the one where he says his visibility is weakest.

Then he sets the whole ranking aside. It does not govern the market today, because there is no rational, universally applied carbon price. Airlines are buying aviation fuel and gas utilities are buying renewable natural gas with no obvious imminent carbon price exposure, early buyers of carbon removal are paying more still, and the people who actually control the resource, the farmers, foresters and food processors sitting on piles of low-value cellulose, have little reason to have researched the comparison and may accept the first workable offer put to them. He says it is possible we are seeing the first signs of a run on the resource, and that the market is many years from real price discovery. His practical conclusion therefore runs against his economic one: the mess is appropriate at this stage, and what is needed is more experimentation rather than an early winner.