Microalgae-derived biochar for durable soil carbon sequestration

Overview

This solution provides a scalable pathway for durable carbon sequestration in agricultural soils by producing biochar from microalgae biomass. Microalgae cultivation avoids competition with food production by using non-arable land and a wide range of water sources, including brackish and seawater. The process generates protein as a high-value co-product, with the remaining deproteinated biomass converted into biochar that can be added to soil for stable, long-term carbon storage.

The approach addresses a key limitation of conventional carbon farming: soil organic carbon is constrained by the amount of organic matter present and can be depleted by microbial decomposition and extractive agricultural practices. Biochar resists decomposition, enabling carbon sequestration that persists for hundreds of years while also supporting agricultural productivity.

Technical specifications

Cultivation system:

• Low-cost microalgae farming developed over 16 years of research
• Operates on non-arable land using brackish water, seawater, or other non-freshwater sources
• High-yielding microalgal strains with demonstrated productivity of 70 tonnes dry weight per hectare per year
• Large-scale commercial farms established in Australia, Oman, Singapore, and Vietnam

Biomass processing:

• Proprietary protein extraction technology producing high-value vegan protein or feed supplement
• Low-cost pH-induced flocculation and biological harvesting methods
• Automated solar drying for the deproteinated biomass
• Pyrolysis conversion of residual carbon-rich biomass into biochar

Soil application:

• Biochar applied to three agricultural soil types: horticulture, grasses, and wheat
• Designed for compatibility with traditional carbon farming approaches using organic matter
• Monitoring of total soil carbon and agricultural biomass yields over a six-month validation period

Technology readiness level

The microalgae cultivation and protein extraction technologies have been validated through commercial-scale farm operations across multiple countries. The biochar production and soil application pathway is currently at the pilot validation stage. The planned project will produce one tonne of microalgae at the UQ Algae Energy Farm, extract protein, manufacture biochar via pyrolysis, and apply it to three soil types to measure carbon sequestration and crop yield improvements over six months.