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.
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.
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.
Late last spring, the BRDI team began acquiring testing apparatus and field equipment needed for torrefaction, drying, and briquetting of biomass at a test site located on Green Diamond property at Big Lagoon. The area, a demolished mill site, consisted of dilapidated cement, old iron railings, and overgrown shrubs. Drawings had already been prepared for electrical lines, equipment placement, and emergency evacuation locations for the test site, so site set up proceeded quickly.
From right to left: the torrefier trailer, the biomass drying unit, and the homemade chip screener used to sift feedstocks to acceptable chip sizes.
The torrifier was a pilot unit custom-built by Norris Thermal Technologies (NTT) and hauled on a trailer over 2000 miles from Indiana. This was the largest piece of equipment on site and was the main focus for our summer testing of feedstocks at various temperatures and dwell times. NTT also provided a drying unit, which was purchased by BRDI for future biochar field-testing. This is the same type of drying unit used in many industries, including food and agriculture. BRDI’s application of the dryer was unique in that it used waste heat from the torrifier to dry the feedstocks to varying degrees of moisture content. The team found that moisture content in the woodchips, hard to control due to the combination of summer rains, early fog, and blazing mid day heat, had a significant impact on torrefaction. Moisture content in samples also affected the briquetting of the woodchips. Dry feedstocks of small particle sizes were observed to form dense briquettes of uniform size. Briquettes made of larger wet chips tended to crumble easily, and if the moisture content was high, the bricks expanded and deformed. In addition, because water is incompressible, too much moisture could damage the process mold and hydraulic pistons used to densify the woodchips into briquettes.
The summer testing team from left to right: Yaad Rana, Andy Eggink, David Carter, Greg Pfotenhauer, Kyle Palmer, Anna Partridge, and Marc Marshall.
Overall, testing was successful and the BRDI team has a plethora of samples to analyze in the lab. An exciting year is expected, as analysis is performed in preparation for continued testing using full-scale equipment next summer.
SERC 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.
As reported previously, SERC is leading the biomass conversion technology demonstration portion of the Waste to Wisdom project. Waste to Wisdom is examining the entire biomass supply chain, from collection, transportation, and pre-treatment of the material in the woods, to the conversion of the material into energy and other marketable products. Our role is to oversee the testing and evaluation of three biomass conversion technologies: a biochar unit, a briquetter, and a torrefier.
We are pleased to announce that the Norris Thermal Technologies (NTT) of Tippecanoe, Indiana is joining the project as the torrefaction research and development partner. SERC conducted a competitive selection process involving 10 firms currently operating in the biomass torrefaction space. NTT’s proposal stood out due to the readiness of their team’s technology and their ability to field mobile torrefaction systems at two different scales within the project’s budget and schedule constraints.
NTT will provide a pilot-scale torrefaction unit (see photo at right) for field-testing during the summer of 2015. This unit, which was recently operated alongside two other biomass conversion units in a demonstration sponsored by the Washington Department of Natural Resources, is trailer mounted and will be modified and then delivered to a forest operations site of our choosing near Arcata, CA.
After completion of pilot testing, NTT’s team will build a larger torrefaction reactor of the same design and retrofit it into a shipping container. NTT will then ship this containerized unit to Arcata for testing at a forest operations site and provide an operator for testing. Testing of the larger unit is currently scheduled for the summer of 2016. We are looking forward to continuing our biomass conversion research efforts with such a strong industry partner and we are confident that the torrefaction research objectives of the Waste to Wisdom project will be met through collaboration with NTT.
Biochar unit with instrumentation installed for testing.
In late July, Marc Marshall, Mark Severy, and I traveled to Pueblo, Colorado to conduct testing on a biochar production machine manufactured by Biochar Solutions Incorporated (BSI). The purpose of our three-week trip was to collect experimental data for use in evaluating stand-alone operation (i.e. without an external source of energy to power the process) of the biochar unit as part of the BRDI project.
Infrared image of biochar unit flare during operation.
Biomass conversion technologies (BCTs), such as the BSI biochar machine, can create higher market-value products in near-woods environments, justifying the transport of these products to market. This in turn could allow fuels reduction and forestry residual management projects to be implemented in greater numbers thereby reducing greenhouse gas emissions and the risk of catastrophic wildfires. One of the goals of the BRDI project is to explore whether stand-alone operation of BCTs improves the economic and environmental benefits of removing slash and other woody residues from the forest.
We spent the first week in Pueblo installing instrumentation on the machine and setting up the data acquisition system. During the second and third weeks, we conducted experiments producing biochar with various biomass feedstocks.The variations in feedstock included tree species, particle size, anatomical distribution, percent contamination, and moisture content. Additional experiments led to design changes in the feedstock drying system and the air injection system for the flare.
The machine generates significant heat while operating (see photo at right). Some of this thermal energy is used for drying feedstock and some is used to preheat fresh air that is injected into the flare for complete combustion. Beyond the heat used for those purposes, there is a significant amount of high quality thermal energy that could potentially be used to generate electricity to power the machine at a forest landing site. Over the coming months, we will analyze the data and evaluate technologies that could be paired with the biochar machine to generate process electricity for stand-alone operations in near-woods environments.