Estimated read time: 5 minutes
Key Points:
- ABC has invested more than $2 million in the search for more outlets and value-add options for hulls and shells
- Researchers are exploring the use of shells for industrial and bioenergy uses
- There is opportunity to integrate shells directly with plastic to make a wood/plastic composite
- The quality of hulls and the lack of foreign materials is an important component to maximize their value for other uses
In the California almond industry, the numbers around kernel production and biomass continue to be on the uptick. In addition to a predicted 3 billion pound crop,1 estimates from the 2020 harvest forecast that this crop year the industry produced:
- 1.9 billion pounds of shells,
- 4.8 billion pounds of hulls, and
- 4.3 billion pounds of tree woody biomass.
Processors and marketing experts have done a phenomenal job of securing homes for the nuts to meet an ever-growing domestic and international appetite for almonds. The almond industry also has done well in finding outlets for the coproducts coming out of the orchard, with hulls and shells most often going to the dairy industry and thanks to growing adoption of Whole Orchard Recycling.
As almond coproduct volume grows and the dairy industry in California slims, however, the industry is asking itself, “Can we diversify and find higher value uses of hulls and shells while continuing progress toward our Almond Orchard 2025 Goal to achieve zero waste by putting everything grown to optimal use?”
A breakout session at The Almond Conference (TAC) 2020, hosted by the Almond Board of California (ABC) last December, was devoted to answering that question.
Traditionally, shells have been used as bedding for dairy cows.
Where we are today
In the past five years, ABC has invested more than $2 million in the search for more outlets and value-add options for hulls and shells, according to Guangwei Huang, associate director of Food Research and Technology at the Almond Board.
ABC’s Biomass Workgroup (made up industry members and allied stakeholders) recently started a comprehensive assessment to develop future strategies and priorities around developing new markets for almond biomass.
Among the potential markets for hulls and shells, some could offer greater price points for the industry if the barriers to these markets do not prove too high:
- University of Minnesota researchers have processed hulls and included them in several prototype food ingredients that may be used in antioxidant beverages (green tea, coffee), functional emulsifiers (used in salad dressings and bakery products), antioxidants and dietary fibers. These novel food grade applications could significantly increase the value of hulls. Understanding the cost competitiveness of hulls, the ability to meet quality specifications and the potential volume of this market are under assessment next.
- Researchers are exploring the use of shells for industrial and bioenergy uses. Almond shells are roughly 50% carbon, a unique physical property that allows them to be converted into biochar, torrefied shells, specialty carbon, biofuels and synthetic gas. Biofuels and synthetic gas are used for heat or electricity generation, whereas biochar may have benefits as a soil amendment and specialty carbon can add value through applications such as carbon black, activated carbon, batteries and gas storage.
- There is opportunity to integrate shells – which are fibrous – directly with plastic to make a wood/plastic composite. Torrefied shells can also be integrated into plastics to enhance their properties.
- Research is also considering the use of hulls and shells in combination with green residues from vegetable farming to allow for soil nitrate immobilization, soil disinfestation, and to provide an alternate for soil fumigation for strawberry growers.
“Economics is a big factor that motivates our research programs,” said ABC’s Chief Scientific Officer Josette Lewis, Ph.D. “Finding more value for hulls, shells, and woody biomass is critical to the profitability and sustainability of our industry.”
Creating energy from shells
North State Hulling is a nonprofit grower cooperative founded in 1968. In 2018 – having outgrown its original facility in Chico – the company acquired 477 acres near Hamilton City in Glenn County. The new complex includes a new processing facility, 100 acres devoted to stockpile and biomass storage, and a planned state-of-the-art biochar facility.
During the TAC 2020 session, North State Hulling General Manager Mayo Ryan said it took two years to identify the right technology to burn almond shells, generating synthetic gas that fuels both microturbines to produce electricity and large-capacity almond dryers. The pyrolysis units produce high-quality biochar that could be used as a soil amendment and for soil carbon sequestration. While much work and planning went into that process, from a financial standpoint installing a biochar facility that uses almond coproducts makes good financial sense: Ryan estimated that the cost of the facility will be paid off in four years or less.
“We won’t have a power bill for the foreseeable future,” he said. He expects the whole system to be up and running later this year.
Ryan said “just about anything” can be burned in the biochar machines, including almond trees that have reached the end of their productive lifespan.
“That really closes the loop when it comes to harnessing the carbon in trees and putting it to good use,” he said. “It’s a perfect carbon cascade taking almond shell and woody biomass, creating biochar with it and putting it back into local almond orchards.” biomass is critical to the profitability and sustainability of our industry.”
