Biomass to Energy: How One Agriculture Waste Solution is Generating Renewable Power

When VGrid Energy Systems hung its shingle, its plan was to sell renewable power sourced from agricultural waste to the grid. That plan has swung into play, but the California company’s team soon learned they could make more than clean electricity through their process.  Today the masses of crop residue fed into VGrid’s gasifiers are also transformed to products from cattle feed and cat litter deodorizer to liquid fertilizers.

At high level, here’s how it’s done: Gasification converts biomass into carbon, which creates gas that runs engines to make electricity. When the gas cools, it condenses to liquid, which goes into the fertilizers. The clean carbon [or biochar] left from the high-temperature conversion process goes into the animal feeds and odor-control applications like the cat litter, among product types.

Creating commodities from agricultural waste has its environmental advantages, with the plants themselves delivering these gains during their lifetime. They sequester enormous volumes of climate-warming carbon through photosynthesis. But when they die, they release the stored carbon back into the atmosphere.

“So rather than let dead biomass decompose and generate emissions, we convert it into electricity, which is rendered carbon-negative because the biochar byproduct stores the captured carbon underground,” says Greg Campbell, VGrid CEO.

The compact, stackable units can produce a kilowatt hour (kWh) of electricity on about a quarter acre. Campbell says that’s about five percent of the space a typical solar array would occupy to generate the same output.

VGrid has 17 systems up and running, with one system able to make 750,000 kWh of electricity a year; 150 tons of biochar; and 50,000 gallons of liquid product.

So far, the sole feedstock is pistachio shells from the Wonderful Company, and only a relatively small portion of the 100,000 tons of shell generated each year. But Campbell, who says Wonderful has signed a letter of intent to supply a “substantial” fixed volume, anticipates the shells sent his way will keep VGrid going for the next few years.

The global ag company is just the partner VGrid was looking for. As large-scale growers they have both plenty of waste and use for the land-enriching applications made from those discards.

VGrid operates two systems for Wonderful, with plans to scale to 30 of them over 10 years and to sell the resulting electricity to Pacific Gas and Electric (PG&E).

Pistachio shells are proving to be good feedstock. They have a low percentage of ash, so they generate an ultra-pure biochar compared to almond shells, corn stover, and some other crops.

And due to the shells’ hardness, the biochar byproduct stands up well to erosion when it functions as a water filter—an increasingly popular application due to its ability to absorb and trap contaminants.

 But Campbell is eyeing other feedstocks that his team has tested and found to perform well, with a few being grass clippings, forest waste, seaweed and, on the non-plant side, cow manure and human biosolids from sewage plants.

The National Renewable Energy Laboratory (NREL) ran a 700-hour demo looking at pistachio shells, confirming VGrid’s claim—the technology generates clean electricity efficiently and at scale, with biochar permanently sequestering carbon and more than offsetting the remaining emissions.

Research done elsewhere found the liquid products increase crop yields by 15% to 60%. And third-party studies conclude that biochar in some farm animal feeds improves digestion and binds toxins.

VGrid’s original business plan was to sell equipment to farmers to use themselves.

“I thought that was a tall ask, so I came up with the idea to sell electricity as a service where we would own and operate the equipment. [Farmers] would provide waste, and we would make electricity to sell to the utility,” Campbell recalls.

Biochar became the first byproduct, with multiple applications quickly becoming clear.  The liquid byproduct and its potential were discovered more through serendipity.

“We did not even know what it was at first, but when we started testing and analyzing it, we determined it had good use cases,” Campbell says.

“What I really like is that [our model] is its own circular economy. We are not wasting anything.  We are getting everything we can out of agricultural discards.”

Demand for nuts, seen as an easy way to get good protein, is steadily climbing.  Wonderful is growing more pistachios than ever to keep up. But the resulting waste is putting pressure on the global ag company and the whole industry. That pressure is especially felt in Wonderful’s home state of California, which banned open field burning of crop waste and set a target to reduce organics to landfill 75% by 2030. Farmers are rushing to find alternative disposal methods for their wastes, says Mike O’Banion, director of Operations, The Wonderful Company.

Wonderful has sent shells to cement manufacturers to heat their kilns for years, happy to find a home for its discards while helping cement makers move away from coal. But now the VGrid partnership provides another and better outlet.

“V-Grid provides a sustainable solution for converting pistachio shell into drastically higher value outputs than through other outlets. So, they not only provide a needed disposal service, but allow farmers to generate better financial return,” O’Banion says.

Campbell sees opportunity as more states and countries spring forward to try and heal a warming planet. On a global scale, COP28 adopted a goal to triple renewable energy capacity by 2030. Agricultural waste could be a resource to help achieve that goal, he says.

As the clamor around climate change amplifies, he has his own goal: to bump the number of bioservers VGrid owns and operates from 17 to 1,000 by 2030.

He says 1,000 systems could divert 1.5B pounds of waste biomass a year, removing 440,00 tons of CO2 emissions. Replacing fossil via renewable energy generation could offset another 180,000 tons of emissions.

An electrical engineer by trade, Campbell first moved into renewable power and carbon capture technologies after coming out of retirement. The former business owner and long-time entrepreneur was worried about what scientists were uncovering about rising temperatures.

“My purpose at this point in my life is to contribute as much as I can to reverse climate change,” he says.

There’s a lot of work to do in a short time.

“It’s too late to stay within the 1.5 degree warming limit set by the Paris Agreement simply by cutting emissions. Carbon removal is the only chance we have. That’s why you will see more technologies coming online like direct air capture and what we do.”