Rationale

Biochar can be defined as a charcoal produced for some biological purpose; to enhance soil fertility, as a livestock feed additive, for soil remediation in case of contamination, or to reduce nitrate and phosphate levels in agricultural water runoff. For such uses, particularly for soil fertility, the molecular structure of the char matters.

Plants have evolved over hundreds of millions of years to obtain their nutrients from topsoil, which is made of decomposed biomass (humic matter) and minerals. The minerals are mostly positively charged, while the humic matter is negatively charged. Hence they bind together to form fertile topsoil. This happy marriage makes these minerals available to plant roots, particularly the more shallow roots of agricultural plants.

If we want to produce a biochar that optimally enhances soil fertility, we might start with the assumption that it should be as similar to humic matter in molecular structure as possible. Why? Because soil biochemistry, and the plant life it supports, will likely respond to such a biochar in the same way as they respond to humic matter. Soil, soil microorganisms and plants have evolved symbiotically over eons. This complex, mutually supportive ecosystem will not adapt to any novel idea simply because it seems good to us. Rather we must ensure our agricultural innovations are adapted to soil ecosystems.

Scientific research supports this simple assumption. The cation exchange capacity (CEC) of biochar, its ability to retain plant nutrients, depends on its molecular structure. Biochar particles produced at low temperatures will have high CEC levels because of the negatively charged OH functional groups on its molecular surfaces.¹

Humic acid model — Model humic acid molecule showing OH functional groups

The molecular structure of char is largely determined by pyrolysis processing temperature and residence time. Biological decomposition, which produces humic acid, is a gentle process. If we want to mimic humic acid's molecular structure in biochar, we need precise control over the temperature and residence time of each biomass particle to orchestrate a gentle thermal biomass decomposition. Precise, low-temperature pyrolysis retains the more delicate, negatively charged OH and COOH groups on the carbon backbone. If we want to produce commercial quantities of biochar, we need that control at scale.

This is why we have developed a novel thermal decomposition technology that operates at production scale and gives us precise control over the essential process conditions, so that each particle’s molecular transformation is precisely determined and has an identical signature across all particles produced.

Most production-scale pyrolysis kilns are of 2 types, auger and rotary. Both tumble the feedstock to distribute heat, which is fine for a clothes dryer, but energy intensive and prone to expensive mechanical breakdowns when processing many tonnes of biomass per day. In an auger kiln, residence time can be controlled, but temperature is kept quite high to prevent tar build-up within the auger. In a rotary kiln, residence time cannot be controlled, and in both of these kilns, pyrolysis temperature cannot be accurately controlled because temperature cannot be accurately measured. Hence both are unsuitable to produce a biochar with optimal soil fertility characteristics.

Our approach is designed to lower capital investment, operating and maintenance costs, and builds on heating principles that are proven across a wide variety of industries.

While our design objective was to provide precise thermal decomposition at scale, the technology can be accurately operated across a range of conditions to produce thermally decomposed biomass for a wide variety of purposes, and includes an adaptable post-processing system for quenching, impregnation or activation.

All in all, our technology is designed for financial viability: it can accurately produce multiple end products, including PyGrow, a range of biochars for soil fertility and remediation, animal feed supplements, and activated carbon.

Rationale

References