SPINIFEX TO BIOCHAR - WASTE REDUCTION

Chevron, Barrow Island

Background

Spinifex grows abundantly on Barrow Island and presents a problem to Chevron’s oil and gas operations. Currently, the spinifex is removed and stockpiled, this process poses a significant fire risk and a legacy issue. Because of the environmental significance of Barrow Island, normal control methods such as spraying with chemicals and burning are not an option.

Objectives

Chevron engaged Energy Farmers to conduct a number of trials to look at pyrolysis as a means to reduce the volume of spinifex stockpiled and collected on an annual bases. The trial comprised of three distinct operations:

  • Preparation of spinifex for pyrolysis
  • Pyrolysis of spinifex
  • Emissions from process

After successful completion of the first trial the scope was widened to include dehydrated food waste that is produced on the island and further trials were carried out.

Outcomes

Outcomes of the trials concluded that:

  • High speed grinding of spinifex was excessively dusty and resulted in a product that pulverised and unsuitable for pyrolysis through the Energy Farmer biochar kiln
  • Pulverised spinifex does not feed via an auger
  • Food waste and spinifex can solidify and potentially “plug” augers
  • Light, fluffy spinifex material enables air to enter the pyrolysis zone, resulting in combustion of the material and reduces char yield
  • A high level of particulate was measured in the flue gas, otherwise emissions were acceptable
  • Biochar that was produced exhibited a high pH when produced at high temperatures.

    Based on learnings from the previous trials, EFA proposed to:

  • Explore alternatives for pre-processing of spinifex to produce a more uniform feedstock
  • Modify the existing kiln to a design specifically tailored to spinifex
  • Design and develop an end to end solution including preprocessing, storage and pyrolysis of spinifex into biochar.

Status

Ongoing – final proposal submitted. Proposed plant layout below.

3D model of pyrolysis plant