The idiom, “One man’s trash is another man’s treasure,” is a concept proving true in the tree nut world.

With only a slight intention of a bad pun, the almond industry puts on a hull of a show in their annual production of some 4 ½ billion pounds of almond hulls that generally go to supply nutrition for Western state dairies.

Although ratios vary substantially from orchard to orchard, on average, field weight yields 50% hulls and 14% shells along with field debris and clean almond meats. 

It’s long been understood that there were other potential markets aside from domestic dairies that need nut hulls, particularly China as a major importer of animal feed ingredients.

Hence the effort to pelletize and cube almond hulls for potential Asian buyers. 

The mechanics are relatively simple, but the political protocol is complex and adventurous, starting with the early 2020 signing of a Phase 1 Economic and Trade Agreement, culmination of three years of collaborative effort among the major players in the California almond industry.

The current phase involves market access development for pelletized/cubed almond hulls as USDA-APHIS negotiates requirements on how to qualify companies for the program and develops a list of approved facilities that will export the processed hulls.

 “The opening up of pelletized hulls/cubes to China would no doubt provide another avenue to bring more value to growers who produce almonds,” said Julie Adams, Almond Board of California Vice President of Regulatory Affairs. “Finding higher value solutions for hulls is in line with our effort to put everything grown to optimal use and another step forward to helping the industry effort to achieve a goal of zero waste.”

A recent edition of ABC’s Global Update reported: “China is a major importer of animal feed ingredients (estimated to be the 5th largest global market for U.S. animal feed), and expectations are high that pelletized/cubed almond hulls will be well-received there.

“California dairies have been a steady consumer of the raw hulls. ABC sees the opening of China and the exporting of almond bi-products as a major boost to meeting some of the 2025 Almond Orchard goals.”

Research projects

While that process is taking place, there are several research projects underway to find other new uses for the hulls and shells after the almonds (and walnuts) no longer need them.

“If we can scale this one effort beyond the laboratory, this particular aspect of optimizing bioproducts will translate to a valuable, novel use for almond shells,” according to Bor-Sen Chiou, part of the USDA Bioproducts Research Unit in Albany, Calif.

“We’re currently working under a three-year CalRecycle grant with a manufacturer of plastic packaging to scale up to the torrefaction process of almond hulls with a goal of producing 2,000 tons of torrefied biomass-composites each year,” he says.

Torrefaction is a thermal process where biomass is heated in the absence of air and oxygen and produces a charcoal-like material which helps reduce the use of plastic fillers and carbon black in the production of plastic composites like pallets.

Cryo-ground torrefied almond shells have a lower density than polyethylene and as a filler, help improve stiffness and raise the heat-deflection temperature of the final product.

Resins created in the torrefaction/palletizing process have been injection molded into shipping pallets, producing a darker color and minimizing the use of carbon black. Using torrefied shells for plastic pallets, garbage cans, and disposable utensils as well as a wood-polymer material for fencing has several advantages -- product stiffness is increased; costs are reduced because biomass is cheaper than recycled plastic, and the process creates an outlet for biomass waste consumption.

“The research results are promising for shells to become useful in multiple markets, a renewable resource rather than using a petroleum resource,” Chiou predicts.