How Nature's Own Chemical Reactions Could Power Our Future

Field report

Because nature does. And it might just change everything.

Natural History Photography Archives / Field Collection

Everyone loves "clean energy" these days. It's the miracle solution. The trouble is, it takes a lot of resources and careful engineering to harness it from natural systems, and the process is rarely 100% efficient. Then you have to store the energy, which isn't so easy; it dissipates and finds ways to escape. We use a vast amount of energy that currently comes from fossilThe preserved remains or traces of ancient organisms, typically mineralized in sedimentaryRock formed by the accumulation and lithification of sediment. rock. fuels buried underground. Almost 2% of global emissions come from just powering basic industrial processes. Before you even start thinking about cars or home heating, there is the existing energy infrastructure that has to be cleaned up.

That's why this natural process discovered by researchers at a Pennsylvania university is interesting. Instead of using electricity to split water into hydrogen and oxygen, it uses decomposing plant matter. Raw organic material is highly reactive and breaks down wherever moisture and warmth combine. The researchers have figured out a way to grind up dried plant material into a fine compost, remove the lignin in a bioreactor, and expose the remaining cellulose to water. The oxygen in the water bonds readily with the carbon compounds, so the released energy radiates outward for collection. The process gives off a great deal of heat as well, which is used to run a small generator. It sounds like a triple win: you get clean energy, rich compost, and electricity.

Lead researcher Eric Schraud tells Leigh Collins of Energy Insight that "in our bioenergy process, every metric tonne of plant waste produces 111kg of usable energy and 3.12MWh of electrical energy from the steam turbine." You don't need tanks or pipes for storage either; you can build it all into a unit the size of a garden shed which you put where the energy is needed, and just feed it compostable material.

Schraud says there is lots of it lying around: "It's everywhere — I'm sure the kitchen you're standing in right now has food scraps. [There's] yard waste, fallen leaves, agricultural residue, coffee grounds…" Nine million metric tons of organic waste gets landfilled in the U.S. each year, which Schraud says could produce about one million tons of clean energy annually, and lots of electricity. Energy Insight says, "The size of the potential market for this bioenergy process is vast, limited only by the supply of compostable waste."

Natural History Collection / Field Archive. January 2022

This is where it gets confusing. We have devoted a lot of attention to bioenergy production, noting how much energy it takes to properly process organic waste — about 13 to 16 kWh per kilogram of material, much of that currently powered by fossilThe preserved remains or traces of ancient organisms, typically mineralized in sedimentaryRock formed by the accumulation and lithification of sediment. rock.-fuel electricity. The traditional composting process requires constant turning and aeration because microbes demand oxygen to break down cellulose, so after the microorganisms separate the carbon from the plant matter, they release CO2 as a byproduct.

And the compost feedstock often comes from industrial agriculture, an ecologically damaging process on its own. So this bioenergy system is feeding a very problematic input into its generator.

But it's waste, you might say; they are not doing this with freshly harvested crops. They are keeping it out of landfills. The problem here is that organic waste is easily composted and returned to soil, with a carbon footprint that's one-twentieth that of producing synthetic fertilizer. It's valuable stuff. Schraud says they are paying $700-800 per metric ton. To paraphrase ecologist Alex Steffen, there is really no such thing as organic waste; it is just useful nutrients in the wrong place and should never be in landfills. It only exists because there are weird things happening in the waste management market now, where food scraps from restaurants are being trucked to distant landfills instead of local composting facilities.

But the biggest problem is that every pound of organic waste that is burned for energy rather than returned to soil is likely a pound of compost that has to be replaced with synthetic fertilizer made from fossilThe preserved remains or traces of ancient organisms, typically mineralized in sedimentaryRock formed by the accumulation and lithification of sediment. rock. fuels and then zapped with kilowatts of electricity. As Carl A. Zimring noted in his book on waste, recycling, "absent a cap on primary material extraction, does not close industrial loops so much as it fuels environmental exploitation." We have to compost it all and use less synthetic input.

I was going to reach out to soil ecology expert Paul Martin for a comment about this, but he beat me to it with a post on his research blog where he pulled no punches:

Organic waste shouldn't be burned for energy instead of composted; it is useful stuff. This whole thing is silly.