The trials have been ongoing for several months and could reach 500 acres, A&B spokesman Darren Pai said Thursday. A map showing possible uses of old Hawaiian Commercial & Sugar Co. fields, released during the Maui Energy Conference in March, showed “Biogas Feedstock Crop” on land near the Kahului Airport and Spreckelsville.

HC&S, a former subsidiary of A&B, shut down operations in December, which opened up 36,000 acres of former sugar cane fields. A&B has said that it is developing various diversified agricultural ventures on the old sugar cane land, and announced in May that it had set up wholly owned subsidiary Kulolio Ranch on 4,000 acres in Hamakuapoko to raise cattle for Maui Cattle Co. partners.

Last month, A&B announced a partnership with Oakland, Calif.-based TerViva to produce biofuel from pongamia trees on 250 acres in north Kihei/Maalaea. A&B CEO Chris Benjamin said in May that the partnership to produce seed oil could expand to 2,000 acres.

Pongamia, however, will not be powering the anaerobic digester at the Wailuku-Kahului Wastewater Reclamation Facility near Kanaha, Pai said. The pongamia project is “still in the early stages,” and A&B has not decided on processing facilities for the seed oil, he said.

But A&B is “focusing on crops that grow in rows and can be mechanically harvested, such as sorghum and corn” for Anaergia Services Maui All Natural Alternative’s power project at the wastewater treatment plant, Pai said.

“We will rotate these plantings with cover crops and legumes to fix nitrogen and other nutrients in the soil,” he added.

Pai said that “initial trial plantings of corn and sorghum have been encouraging.” The trials at this stage will be used to determine yields, the economics and “what it will take to scale up the production,” he said.

Both the development of biofuel for the Anaergia project and the pongamia TerViva partnership are programs of A&B subsidiary Central Maui Feedstocks LLC, which was organized in November. The company falls under the purview of Rick Volner, the former HC&S general manager who currently heads up A&B’s diversified agricultural initiatives, said Pai.

“Central Maui Feedstocks is focused on growing energy crops,” Pai said. “We are conducting trials to learn more about the yields and costs involved with growing different kinds of energy crops on our former sugar cane lands.”

The company also is “exploring the possibility that these crops may also produce byproducts that can be used as feed and forage for animals,” he said.

Central Maui Feedstocks’ two current programs are separate and not related, Pai said. He said that the terms of the company’s contract to supply energy crops to the Anaergia project are confidential.

An environmental impact statement preparation notice posted last month for the Anaergia project cited the contract with Central Maui Feedstocks. It said that the energy crops would be grown on former HC&S land.

According to the notice, the energy crops would produce methane through a digestion process. The natural gas would be refined on-site and fuel a combined heat-and-power engine to generate electricity for the treatment plant.

Waste heat from the engine would dry solid matter, or sludge. The project would power the wastewater treatment plant but not be hooked up to the Maui Electric Co. grid.

In December, the Maui County Council approved a resolution for a 20-year lease for Anaergia and Maui All Natural Alternatives for a 1-acre site on the treatment plant property.

The environmental review process is expected to be completed by the end of the year, and the project is planned to be operational by the end of 2019.

Anaergia contracted with the county in 2014 to build a waste conversion facility at the Central Maui Landfill. It also has proposed building a $50 million Maui Energy Park in West Maui to grow sorghum.

* Lee Imada can be reached at leeimada@mauinews.com.