Improving a Biochar Production System in Mendocino County

by Kyle Palmer and Mark Severy

For the past three years, the Redwood Forest Foundation, Inc. (RFFI) has produced biochar from small-diameter tanoak trees collected from thinning operations in Mendocino County’s Usal Forest. The Usal Forest ecosystem was disrupted by industrial logging operations throughout the 20th century. Tanoak’s rapid regrowth dominated canopy light, and interfered with redwood repopulation. RFFI is selectively removing tanoak to create the natural space that redwood needs to flourish, and converting the tanoak into biochar to help fund their restoration work.

Biochar, a blackened, solid biomass produced at temperatures above 500°C in the absence of oxygen, is used primarily as a soil amendment to increase water holding capacity, reduce nutrient leaching, and improve conditions for microbial life. (Learn more about biochar on the Waste to Wisdom site.)

RFFI’s biochar production operation has balanced on the edge of technical and economic feasibility due to the high moisture content of the tanoak feedstock and the labor costs required to operate the machine. In 2016, the Schatz Energy Research Center addressed moisture content by installing a biomass drying system that uses waste heat from the biochar machine. This year, the Schatz Center is working to reduce labor hours while improving safety and productivity, by automating key processes on the machine.

A SEM photo shows the porosity of biochar


The highly porous structure of biochar is shown through scanning electron microscopy (SEM) at 600x magnification. This SEM image was taken by Murielle Manka and Marty Reed, using the Humboldt State CNRS Core Research Facility’s FEI Quanta 250 ESEM. The Quanta was obtained in 2012 via a Major Research Instrumentation grant from the National Science Foundation.

In July and August, research engineers Kyle Palmer, Andy Eggink and student research assistant Murielle Manka evaluated baseline labor hours, biochar production rate, and biochar quality produced with the existing system. Throughout these tests, real-time data were collected for gas flow, composition, and electric power demand to help develop the control schemes. Monitoring and automation equipment are currently being installed and performance improvements will be validated in the coming months.

The preliminary results from this study were presented in early September by Murielle Manka and Schatz Director Arne Jacobson at the Agricultural Research Institute’s (ARI) principal investigator’s meeting in Sacramento. Validation test results analyzed this autumn will quantify benefits of the automation system, including any reductions in labor, increases in throughput, and changes in biochar quality.

This material is based upon work supported by California State University Agricultural Research Institute and a grant from the U.S. Department of Energy under the Biomass Research and Development Initiative program: Award Number DE-EE0006297.


Murielle Manka and Arne Jacobson present biochar testing results


Murielle Manka and Arne Jacobson at the September 2017 ARI meeting in Sacramento


BRDI Waste to Wisdom: Results from Preliminary Biomass Briquetting

The Biomass Research and Development Initiative (BRDI) Waste to Wisdom project is studying various pathways to increase the value of forest residuals and decrease transportation costs to bring this underutilized resource into the renewable energy market. Densifying waste biomass into briquettes during forest operations may achieve both of these goals by converting it into a valuable heating fuel that is easily transported due to its high density and low moisture content.

SERC Project Manager Dave Carter operates the briquetter.

SERC Project Manager Dave Carter operates the briquetter.

Last April, SERC engineers, alongside partners from Pellet Fuels Institute and RUF Briquetting Systems, operated a commercial briquetter with a variety of feedstocks at Bear Mountain Forest Products’ manufacturing plant in Cascade Locks, Oregon. Electricity consumption and biomass throughput data were collected in the field, while a pallet containing feedstock and briquette samples was shipped to SERC for material analysis. Back at SERC’s lab, the samples were sent through a suite of tests to assess the quality of each briquette and determine which feedstock properties influence the end product’s characteristics, such as density, durability, grindability, and moisture absorption.

Briquettes produced from chipped biomass exit the briquetting machine.

Briquettes produced from chipped biomass exit the briquetting machine.

Results show that this briquetting system increases the volumetric energy density of chipped biomass by nearly 250%, producing briquettes with an average packing density of 720 kg/m3. Feedstocks with moisture content exceeding 15% produce lower density briquettes, which expand in height after exiting the briquette press. High moisture content, however, does not significantly impact briquette durability. Instead, the feedstock’s particle size distribution has the greatest effect on briquette durability. Feedstocks comprising mainly large particles, especially chipped biomass, do not bind together as well as fine or ground particles. To improve durability, chipped biomass can be combined with sawdust, which increases briquette durability two-fold and results in briquettes with a binding strength similar to those produced from pure sawdust.

These results help frame and guide our future work with biomass densification. In the next stages of this project, the multidisciplinary BRDI research team will investigate whether the upstream energy investments in drying and particle size reduction are worth the payback when bringing briquettes to the heating market.

BRDI Waste to Wisdom: Remote Power Generation and Summer Testing

BRDI-2-webSERC continues work on the BRDI Waste to Wisdom project, a three-year, multidisciplinary project to study pathways to convert forest residuals – or slash piles – into valuable energy and agricultural products at processing sites near timber harvest locations. Many of the potential processing sites do not have access to electricity, so SERC has been analyzing various methods to power this industrial equipment in remote locations. With help from the Environmental Resources Engineering capstone design course, SERC completed a technical and economic feasibility analysis comparing various remote power generation technologies, including waste heat recovery, biomass gasification, solar photovoltaic, and others. The results from this paper study indicate that a biomass gasifier is likely to outperform the other technologies in terms of mobility, cost, reliability, and environmental impact. After presenting these finding to the U.S. Department of Energy, the funding agency for this project, we procured a mobile, 20 kW biomass gasifier (similar to the one in the photo above) from All Power Labs in Berkeley, CA. Once it arrives, we will begin a series of tests to evaluate whether its performance will meet the requirements to operate in the demanding conditions of a forest-landing site.

With the gasifier being fabricated and a torrefier and a briquetter being prepared for shipment, it’s shaping up to be an exciting and eventful spring and summer of biomass fieldwork. SERC will lead the effort to test the torrefier, briquetter, and gasifier generator set at a forest-landing site in Big Lagoon, CA. We will measure the performance characteristics of each machine with a variety of biomass feedstocks recovered from timber harvest operations here in northern California. In addition to testing these machines individually, their synergy in an integrated system will be evaluated by connecting them together. For example, we will conduct experiments to densify torrefied biomass and to evaluate whether the gasifier generator set can reliably provide electricity to the other machines. Having these three commercial-scale technologies at a single site provides a unique testing and demonstration experience.

To prepare for this fieldwork, we have been busy developing the testing matrices, procuring feedstocks, detailing our instrumentation plans, preparing our data analysis tools, and coordinating associated logistical issues. The entire BRDI team is looking forward to a productive season of data collection and analysis that will help address the key issues posing a barrier to recovery and utilization of forest residual waste.

Aqueous Phase Reformation

Researchers at SERC are studying alternative pathways for biomass energy to displace fossil fuels in existing high-efficiency power plants. Chemical reactions can harness waste heat to convert biomass into a hydrogen-rich syngas, displacing fossil fuel consumption. Modeling work at SERC estimates that integrated systems can produce between 5% and 100% of a power plant’s fuel requirement from biomass, depending on the quality of the waste heat resource. If applied to internal combustion engine power plants, blending hydrogen-rich syngas with natural gas additionally reduces untreated nitrogen oxide (NOx) emissions by up to 95% and increases engine efficiency by up to 25%.

Over the past year, SERC’s Dr. David Vernon led a research team to study aqueous phase reformation (APR) of plant-derived sugars to produce a hydrogen-rich syngas. This project, funded by the California Energy Commission, investigated the potential to use this low temperature reformation process to recover waste heat from natural gas power plants. SERC engineers designed, built, and tested a benchtop chemical reactor to convert aqueous sorbitol (C6H14O6) into an energy-rich gas consisting of hydrogen, carbon dioxide, and methane. Sorbitol, a sugar alcohol, was selected as the feedstock because it is easily produced from glucose, a biomass derivative, and reforming sorbitol produces hydrogen at a faster rate than reforming glucose.

Testing was completed in April. Our results showed that APR is able to convert up to 94% of the input sorbitol into a hydrogen-rich gaseous fuel. By synthesizing our own catalysts at SERC, we were able to produce a gas containing 64% hydrogen by volume. Furthermore, the output liquid and gas were found to contain 46% more chemical energy than the input feedstock.

Based on these promising results, we conclude that it is feasible to use APR in waste heat recovery applications. We have applied for additional funding to continue this work. Next, we plan to use crude glycerol, a byproduct of biodiesel production, as the feedstock. Our economic models predict that converting crude glycerol will significantly reduce the lifecycle costs of the system, making this process more cost competitive than other waste heat recovery technologies such as organic Rankine cycles.