Briquettes made from forest residues. Photo: Schatz Energy Research Center, Humboldt State University
The Conversion Technologies team proposes to develop and test three biomass conversion technologies, specifically a biochar production system, a torrefier, and a briquetter. Project activities will focus on the development of conversion technologies that are energy-independent, compatible with a wide range of biomass feedstocks, and are ready for commercialization. The systems to be developed will be diverse, innovative, and cost-effective in keeping with Biomass Research and Development Initiative (BRDI)program goals. The conversion technologies team will consider three technologies aimed at increasing the value of biomass feedstock and reducing transportation costs to deliver competitively priced products to market. The technologies being assessed include (i) production of biochar, which can be used as a soil amendment and carbon sequestration tool or as an input for other products such as activated charcoal, (ii) a torrefaction (pyrolysis) system producing torrefied biomass that can be used as a direct substitute for coal in existing power plants and (iii) a densification system that produces briquetted biomass fuel for use in industrial power or heat production.
In order to contribute to a reduction in transport costs, each of these technologies must be adapted to operate using multiple feedstocks located at or near forest landing sites where the forest residues are located. In two cases, gasification/biochar and pyrolysis/torrefaction production, the respective technologies require scaling to achieve the economies of scale necessary for profitability.
Biomass densification will make it economically feasible to remove and market forest residues that are currently piled and burned or left in situ to decompose. For example, torrefied woody biomass has a mass energy density of 20.4–22.7 GJ/bone dry ton, as compared with 910 GJ/ green ton for biomass typically delivered to local power plants at 50% moisture content in northern California. Densified biomass also offers value in the form of non-energy, bio-based products, such as biochar. In addition to its marketability as a soil amendment or activated charcoal product, biochar is also used by natural resource industries for the restoration of damaged and disturbed soils at logging and mining sites. Biochar production via gasification has been well characterized, but like the other technologies to be developed under this project, it has not yet been adapted for inforest production at commercial scale.
Standalone operation is critical if these technologies are to operate successfully at or near forest operation sites. While the requirements vary by technology, all three conversion technologies included in this project will require heat for feedstock drying and processing and electricity for motor drives, compression, and/or control system operation. Ultimately, achieving a successful standalone field operation will require that all of this energy come from onsite biomass and/or waste heat from existing field site operations rather than from diesel fuel.
Using energy from onsite resources can make or break the economics of biomass conversion technology use. Collection and comminution of biomass for hogfuel production (i.e., a common baseline product of forest residue biomass) requires about 1.5 gallons of diesel fuel per bone dry ton (bdt). Additional 2.9 gallons of diesel are needed to make a round trip to deliver each bdt of chipped biomass to a power plant for a one way distance of 50 miles. Onsite conversion of the hogfuel into torrefied biomass can reduce the transportation fuel requirements to one gallon per bdt. The fuel savings and increased market value of the end-product can result in an economically favorable outcome, but this is true only if the gains are not offset by the cost of purchasing fuel to operate the torrefaction and densification equipment. For example, a torrefier system at commercial scale has an expected electricity consumption of 70 kWh/bdt. If this electricity were supplied by a diesel generator, approximately 9.2 gallons of diesel fuel would be required per bdt. This clearly more than offsets the transportation fuel savings from torrefaction, so standalone operation is imperative. Energy requirements of biochar and briquetting systems are different, but the same principle applies: the economics improve greatly when the energy needs of the processing equipment can be provided independently on site.
Options for generating electricity onsite using available forest residues include producer gas from biochar production, waste heat from the torrefaction process and other onsite equipment such as diesel powered grinding or chipping machines. Organic Rankine cycle generators show promise for converting low-temperature waste heat into electricity. Electricity generated onsite will be used to power the material handling, densification, instrumentation, and control systems used in the conversion technologies in the project.
Since all three biomass conversion technology processes require electric power and heat for drying, co-locating two or more of the biomass conversion technologies can offer important synergies. For example, biochar production yields energy-rich producer gas in excess of that needed to power the biochar process itself. The surplus gas could be combusted and diverted to an energy recovery device (e.g., a heat exchanger) to condition the excess energy into a form (e.g., hot water or oil) that would be input into a heat engine to power an adjacent torrefier or briquetter.
The proposed project is novel and innovative in multiple ways. Research activities will emphasize strategies to adapt all three technologies for mobility and standalone, off-grid operation features, which are yet to be commercialized and integrated into modern, efficient forest waste-to-heat equipment. Also, operating the three technologies at a single site will allow operation under consistent conditions using identical feedstocks, yielding performance data to facilitate the comparison of the three technologies.
The three technology developers participating in the Conversion Technologies team each bring merit to the project with diverse equipment designs and applications. This diversity in approaches can provide lessons learned across technology platforms and enable synergies between platforms that can help advance commercialization efforts for all of the technologies.
Learn more about the subtasks in this technical area:
- Scale up and development of field ready unit
- Testing and field deployment
- Adapt unit for field readiness and operation
- Scale up unit, and field deployment and testing
- Assess suitability of commercial briquetting unit for field operation
- Operate a briquetting unit
- Assess potential to utilize waste heat for energy input needs
- Test biomass conversion technologies using a variety of residue types and tree species under field conditions
- Perform data analysis and report on outcomes
Webinars
Biochar Production Using Forest Residuals
