A demonstration of the Iron Wolf 700B machine which grinds up almond trees in the orchard Farm Press file photo

A demonstration of the Iron Wolf 700B machine which grinds up almond trees in the orchard. Farm Press file photo.

Almond Board research explores alternative uses of by-products as markets shift

The changing markets for almond by-products have led the Almond Board of California to step up its research into alternatives to managing orchard removal waste, plus hulls and shells.  ABC–funded research is delving into the area of bioenergy, or bioeconomy, to maximize the potential value of almond biomass as bioenergy feedstock. 

The changing markets for almond by-products have led the Almond Board of California (ABC) to step up its research into alternatives to managing orchard removal waste, plus hulls and shells.

The reduction in cogeneration facilities is making it more expensive and difficult to find homes for the wood waste. At the same time, the value of hulls has significantly declined, as demand from the California dairy industry is decreasing while almond hull production is continually increasing.

Along with investing in research, ABC is working closely with the Almond Alliance of California (AAC), formerly the Almond Hullers and Processors Association, to provide relevant data to assist AAC in its efforts as part of a broad coalition seeking state legislative and regulatory solutions to California’s management of wood waste.

Orchard removal

Traditionally, almond orchard removals have been a large source of materials for cogeneration plants. But due to changes in the electricity market, electricity providers are choosing not to re-sign contracts with cogeneration plants. As a result, there have been several closings of cogeneration plants in the San Joaquin Valley (SJV).

According to the California Biomass Energy Alliance, five plants have closed due to “antiquated contracts that do not cover all of the plants’ costs. Half of the remaining plants are facing expiring contracts. Without new contracts and revenue streams that reward biomass plants for all of their attributes, half the industry will cease to exist.”

With the industry anticipating a significant increase in orchard removals over the next several years based on the natural life cycle of the trees and the continuing impact of the drought, the Almond Board is conducting research on several fronts into alternative uses for almond tree removal biomass.

Whole-orchard grinding research

One of the alternatives for dealing with tree biomass upon orchard removal is grinding up all almond trees and incorporating the tree biomass into the soil, leading to the question of how this additional organic matter affects the soil, and more importantly, how it affects the health of a subsequent almond orchard planted in these soils.

An orchard recycling trial project conducted over six years at the University of California’s Kearney Agricultural Research and Extension Center has shown some promising results, according to Gabriele Ludwig, ABC’s director of Sustainability and Environmental Affairs.

“The results look promising, in that the young trees could handle it, and after three years, we saw benefits to the soil,” she said.

San Joaquin County UC Cooperative Extension Farm Advisor Brent Holtz has led this research. At December’s Almond Conference, Holtz reported on the findings of the orchard recycling project to date.

A key finding is that after three years, positive changes in the soil were noticed, including significant improvement in water holding capacity. This was noticed when the experimental orchard was accidentally not irrigated last summer, and the trees in the ground-up plots had significantly better stem water potential compared to the plots where the removed trees had been burned.

The data also indicated that the ions in the soil, especially harmful salts, might be improved with the infusion of woody organic matter into the soil.

The research so far has shown that the main issues to be resolved include:

  • Ensuring that incorporating the woody biomass into the soil works in different soil types found throughout the various almond-growing regions;
  • How best to grind up the trees and incorporate them into the soil. Variables include equipment, size of chips and emissions associated with incorporating into the soil;
  • Ensuring the ground-up chips don’t harm the new orchard by passing along diseases, other pests or nutrient deficiencies;
  • Understanding the carbon sequestration potential so growers can potentially receive carbon credits; and
  • The cost to growers, as tree removal is no longer supported by the sale of the wood to co-gen facilities.

ABC is now funding additional trials to see if the results can be replicated in different types of soils, to learn how best to grind up the trees and incorporate the material, and to ensure the recycling doesn’t spread diseases.

Bioenergy and value-added alternatives

Almond Board–funded research is delving into the area of bioenergy, also known as bioeconomy, to maximize the potential value of almond biomass as bioenergy feedstock. This approach utilizes newer, more efficient thermal, biochemical, or biological conversion and-or extraction technologies to produce biogas, liquid fuels, biochar, bioethanol, liquid fertilizers, value-added materials, and chemicals from almond biomass.

Biogas and biofuels are clean energy feedstocks. Biochar can be used as a soil amendment. The modified materials can be used as additives to improve properties of plastic containers including garbage cans, flower pots and rubber tires, and the chemicals may be used to make fiberic materials and food-pharmaceutical additives.

There are multiple different thermal processes that convert biomass into energy beyond burning, including gasification, pyrolysis, and torrefaction. Each process, operated at different temperatures, produces different outputs.

  • Gasification – Converts biomass to carbon monoxide, hydrogen, and carbon dioxide at temperatures greater than 700 degrees Celsius without combustion under a controlled amount of oxygen and-or steam.
  • Pyrolysis – Converts biomass in the absence of oxygen at a temperature of 300-700 degrees C. to produce biogas, bio-oils, and biochar. 
  • Torrification – Converts biomass in the absence of oxygen at a temperature of 200-300 degrees C to produce torrefied materials, bio-oils, biochar, etc.

Each of these processes has at least some kind of pilot project somewhere in California (generally not in the SJV) or elsewhere in the country. These processes work at different temperatures and have different outputs.

Some generate biogas that can be burned for energy, some generate biogas for biodiesels, and some generate it for other kinds of bioliquids that may have biopesticide potential.

These processes might also be useful for alternative or higher-value uses of shells and hulls. For years, almond hulls and shells have been put to good use. Almond hulls are a good source of animal feed and typically have a much higher economic value than shells.

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However, with the price of corn coming down and the California dairy industry struggling economically, the value of almonds hulls has decreased significantly.

In addition, increasing almond production creates excessive hulls that need additional outlets. This reality has resulted in Almond Board–funded research focused on new uses for energy or for extraction of compounds useful in chemical processes.

Almond shells are typically sold for animal bedding, but some are shipped to cogeneration plants that combust wood waste to produce electricity. However, the Alliance says the amount of shells going into cogeneration has declined dramatically over the past few years, and currently is a negligible amount. 

Ludwig noted that UC Davis and USDA’s Agricultural Research Service (ARS) have developed some value-added chemistry processes for almond by-products that need to be field-tested.

“A number of private companies have contacted the Almond Board about using almond by-products including wood, hulls, and shells for one or another of these processes for facilities they plan to build or to have shipped outside of California,” Ludwig explained.

There are many questions to be answered about the new bio economy processes.

“We don’t know whether they can meet the ‘new source review’ requirements under the Clean Air Act in California for NOx or PM2.5,” she said. “We don’t know how their carbon criteria air pollutant footprint compares to the current cogeneration systems, and we don’t know how much investment it will take.”

All of these research initiatives need is more time, say Ludwig and AAC leaders.

“With all of these possible approaches, we need to figure out how to make them usable under a wide range of circumstances and sort out any possible regulatory issues,” added Ludwig. “Research on soils, woody materials, trees, energy-biochemistry production in real life just doesn’t happen overnight.”

The call for more time is a key message of a coalition of agricultural and forestry groups that includes the Almond Alliance of California. AAC President Kelly Covello signed on behalf of the AAC a recent letter to State Assembly Budget Chairman Phil Ting that called for the allocation of greenhouse gas reduction funds for the support of biomass energy.

“It is critically important that the existing cogeneration facilities get the funding needed to continue to operate and serve as an integral function in the state’s management of wood waste,” said Covello.

“The greenhouse gas emission reductions from utilizing biomass waste at these facilities are significant and verifiable. Biomass is a very important outlet for the almond industry, and we will continue to work hard with other groups to find solutions to keeping these cogeneration plants operational,” she said. 

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