On a recent Friday, a group of researchers harvested a batch of cucumbers that took about a month to grow at the Waimānalo Research Station. Most of the collected produce was over a foot long and heavy enough to fall from the vines.
They are testing fertilizers made of wildfire-prone invasive plant biomass to see if they can grow food just as well as contemporary products, typically made from fossil fuels.
"So far, things are looking promising," said Naomi Kukac of Simonpietri Enterprises, a Hawaiʻi-based business focused on renewable fuels, innovative solutions and consulting.
The project could lead to a cheaper alternative for local farmers who have long faced rising fertilizer prices heightened by the COVID-19 pandemic, low inventory and sanctions on Russia.
Simonpietri Enterprises is making organic fertilizer from chicken manure, potassium and small amounts of biochar made from invasive grasses and wood waste.
"We use a process called gasification, and out of that process, there is ash that's created when you're using clean biomass," Kukac said. She's talking about pyrolysis, the result of burning wood in the absence of oxygen.
The invasive plants are harvested by Native Hawaiian plant nursery Hui Kū Maoli Ola. Invasive grasses and shrubs make up about a quarter of Hawai‘i's landscape, according to the U.S. Department of Agriculture.
Joelle Simonpietri is the company owner who wanted to go back to her biology roots for this project. She said the goal is to make a comparable product at a comparable cost using clean energy and locally produced materials.
"What I realized is that if we do have this stream of clean biomass, from fast-growing invasive species, then we actually have an opportunity to do something with the ash, too," she said.
"So not just make energy but also make potash for fertilizer. It goes back to those original roots of where the word potash even comes from — it's the wood ash that's leftover after your cooking fire."
Simonpietri hopes the project will help local farmers keep their input costs down.
"I can't guarantee we will always be able to outprice fossil fuel-based, multinational product development — but we're trying," she said.
The company just finished its first crop trial, growing cucumbers at the Waimānalo Research Station and tatsoi at the Pearl City Urban Garden Center. It is now looking for local farmers to try their fertilizer.
Haley McKinnon, a farmer at Ahiki Acres in Waimānalo, uses mainly compost to produce various vegetables.
She pays up to $3,000 a year, plus delivery fees, for about 25 cubic yards of compost — so the price makes a huge difference to her.
"We would probably purchase that much compost three times a year," she said. "If it were cheaper, we would probably triple that amount. We just can't afford it."
McKinnon said she would be open to using fertilizer made of invasive grass biomass.
"I would really like to get connected and I'd be down to trial it out on our farm as well," she said. "Often, like fertilizers, compost actually takes time to see results. It could take years to actually see how it's affecting crops, but we would still be interested to see how it works."
The cost of the fertilizer is still unclear as the company continues its research.
After more testing with farmers, the next phase of the fertilizer project would need approval by state and federal regulators.
