The thick, thorny gorse bush covers 13,000 acres of Hawaiian Home Lands in Humu'ula on the slopes of Mauna Kea, Hawai'i. - Photo: T. Ilihia Gionson

Humu'ula project to clear thorny nuisance, produce biofuel

By T. Ilihia Gionson / Ka Wai Ola

On 13,000 acres of Hawaiian home lands on the slopes of Mauna Kea grows the obnoxious gorse bush – a thick, thorny nuisance that chokes out other plants and takes over landscapes like wildfire. But Duke Kapuniai and his Humu'ula Renewable Energy Partnership are working to return the 'āina to productivity, and in so doing turn the weed into fuel.

A native of Europe and Africa, the gorse shrub was originally brought to Hawai'i in the early 1900s to act as inexpensive fencing to contain cattle. When Humu'ula was being used as ranchland, the gorse was maintained and controlled. But after ranching ceased on the slopes, the gorse ran amok.

Previous natural and chemical attempts to control gorse's spread in the area have met with varied success. Trees planted to shade the gorse out of existence were eventually taken over by the pest. Herbicide spread by helicopter didn't make it to the roots through the thick brush, so while the top of the plant died, it grew back.

This project takes a more direct method to removing the gorse, which ranges from 4 to 6 feet in height – excavators with a rake-like attachment pull the thick bush out, roots and all. Then, using Flash Carbonization technology from Carbon Diversion, the project will convert the gorse into biofuel on site.

The thick, thorny gorse bush covers 13,000 acres of Hawaiian Home Lands in Humu'ula on the slopes of Mauna Kea, Hawai'i. - Photo: T. Ilihia Gionson

A conservative estimate has the project pulling 58 to 72 tons of gorse from each acre, which can then be carbonized and processed into 21,000 to 26,000 gallons of synthetic diesel fuel. The fuel can be used in any vehicle or piece of equipment that uses diesel, including the heavy machinery and processing plant that will be on the project site.

Weed that it is, gorse can grow to a height of four feet in a matter of a year. Because of its quick growth and the extent of the gorse invasion, the project to control the plant on the entire 13,000 acres could take decades. Luckily, as soon as the gorse is removed, the grass that was previously growing in the area sprouts back.

Kapuniai, the project's manager, is starting with 1,000 acres of the most challenging terrain, and has been working on the project since January. His crew is improving the notoriously tough Manā Road so that equipment can be brought up to the site and the product back down.

Kapuniai's team consists of Native Hawaiian men and women of various ages and backgrounds from around Hawai'i Island. The workers are excited about being able to earn a living while helping Mother Earth.

"I'm grateful to be working, and for the opportunity to give back to the 'āina while producing renewable energy," said Daniel Kahawaii, an equipment operator with the project. "I love my job."

The Humu'ula Renewable Energy Partnership Project is managed by the nonprofit 'Ōiwi Lōkahi O Ka Mokupuni O Keawe with its partners, the state Department of Hawaiian Home Lands, Carbon Diversion Inc., Bacon Universal, Pacific Crane and Equipment Inc., and Innovative Tractor Werkes LLC.