How We Produce Biochar

How it works _ Overview

How We Produce Biochar

Pacific Biochar has identified a way to leverage existing infrastructure for biochar production, making for an approach that is cost efficient and quick to scale.  In short, we partner with certain biomass power plants and work together to modify their equipment for production of biochar.  Here is a bit more detail on what that looks like.

Biochar is produced from biomass through a process called pyrolysis (heating at high temperatures in the absence of oxygen). Pyrolysis creates a very stable, solid form of carbon that can endure for thousands of years, making it an ideal technology for scalable carbon removal. 

Pacific Biochar’s biochar is manufactured from forest biomass collected primarily from designated high fire hazard areas in California that are among the highest risk of forest fires. This forest biomass includes non-merchantable forestry thinnings, power line clearings, logging residues, and sawmill residues. Removing excess biomass (fuel) is essential to reducing catastrophic fire danger, which in 2018 generated almost as much carbon dioxide as California’s entire electricity sector and cost the state $24B. The numbers in the past few years are worse.

Much of the excess forest biomass is chipped and then burned at biomass energy plants, producing power for the energy grid, energy that is considered carbon neutral.  Although the power plants are designed chiefly for combustion to maximize energy generation, pyrolysis does occur in the furnace.  But without modification such as outlined below, the biochar produced in the furnace will be burned before it can see the light of day. Through a relatively low-cost engineering upgrade and change of practice, which we call “modification light,” we partner with biomass energy plants to intentionally produce and harvest high quality biochar materials from these facilities.  

Rather than simply upgrading the existing equipment, which we refer to as modification light, there is additional opportunity to leverage the existing infrastructure, which we call modification heavy.  Side-along pyrolyzers can be installed on-site and integrated with the boiler, generator, and emissions cleaning systems.  This is accomplished by installing a pyrolyzer near to the boiler, which is then used to make biochar and wood gas, the wood gas is then piped into the boiler, displacing the need for solid fuel and piggy-backing on the generator and emissions cleaning equipment already in place.

Shovel ready

How We Produce Biochar _ Modification Light

There are many types of boilers utilized by biomass energy plants. We are primarily working with boilers referred to as “stoker grate.”  In these systems, the air draft system designed to keep the fires stoked is sufficiently high velocity to carry bits of charcoal (carbon or biochar) out of the boiler furnace, where it ends up in the emissions cleaning system. In the emissions cleaning equipment, it is common practice that a significant amount of the charcoal is separated from the mineral ash for the purpose of re-injection back into the boiler to be burnt as a valuable fuel. This charcoal material is commonly referred to as “re-injection ash”. Under normal practice it will will never see the light of day.  

Our change in management practice is designed to harvest this re-injection ash, resulting in a biochar material that is very low ash and of high carbon content.  This is accomplished by essentially cutting into the reinjection ash system and installing an alternative pathway that leads to our trucks instead of the furnace. Once intercepted, the pathway to our trucks is briefly described as such: rotary air locks to inhibit air leaking into the system at the connection point, then augers to transport to a silo for storage, then air locks again, then auger system to a truck loading house. Truck loading house is outfitted with conditioner to add moisture to biochar as final step before loading. This general process can be achieved in several ways.  

When this re-injection ash is harvested instead of burned, the change of practice results in the facility either experiencing reduced energy output proportional to the energy value of the biochar harvested, or maintaining energy output by adding extra biomass.  In all instances to date, electrical output is maintained and additional biomass is added proportional to the energy value of the biochar that is harvested instead of burned.  In this way, harvesting biochar allows biomass power plants to increase their throughput and further aid in forest fuel reduction efforts, a major benefit in CA.

The resulting biochar is highly recalcitrant and has a far greater half life than the original materials, verified as removing 2.5 to 2.9 tons of CO2e from the atmosphere per ton of biochar applied.  Biochar has multiple commercial uses at industrial volumes, for example, as a compost additive, a soil amendment, a potting media additive, and in soil remediation.

 

How We Produce Biochar _ Modification Heavy Summary

A dedicated carbonizer (i.e. indirect fired rotary kiln) is installed alongside a boiler-type biomass power plant, and integrated.  Biomass that is fed into the carbonizer is transformed into biochar, releasing gases.  Gases are fed into the boiler where they are burned for energy.