Co-production Of Biochar Research Articles

Distributed biochar and bioenergy coproduction: a regionally specific case study of environmental benefits and economic impacts

AbstractBiochar has been advocated as a method of sequestering carbon while simultaneously improving crop yields and agro‐ecosystem sustainability. It can be produced from a wide variety of biomass feedstocks using different thermochemical conversion technologies with or without the recovery of energy coproducts, resulting in chars of differing quality and a range of overall system greenhouse gas (GHG) mitigation outcomes. This analysis expands on previous sustainability studies by proposing a mechanistic life cycle GHG and economic operating cost assessment model for the coproduction of biochar and bioenergy from biomass residue feedstocks, with a case study for north‐central Colorado presented. Production is modeled as a continuous function of temperature for slow pyrolysis, fast pyrolysis, and gasification systems. Biochar environmental benefits (C sequestration, N2O suppression, crop yield improvements) are predicted in terms of expected liming value and recalcitrance. System‐level net GHG mitigation is computed, and net returns are estimated that reflect the variable economic costs of production, the agronomic value of biochar based on agricultural limestone or fertilizer displacement, and the value of GHG mitigation, with results compared to the alternate use of char for energy production. Case study results indicate that slow pyrolysis systems can mitigate up to 1.4 Mg CO2eq/Mg feedstock consumed, provided a favorable feedstock is utilized, production air pollutant emissions are mitigated, and energy coproducts are recovered. The model suggests that while financial returns are generally greater when char is consumed for energy (biocoal) than when used as a soil amendment (biochar), chars produced through high‐temperature conversion processes will have greater GHG‐mitigation value as biochar. The biochar scenario reaches economic parity at carbon prices as low as $50/Mg CO2eq for optimal scenarios, despite conservative modeling assumptions. This model is a step toward spatially explicit assessment and optimization of biochar system design across different feedstocks, conversion technologies, and agricultural soils.

Steam Pyrolysis and Catalytic Steam Reforming of Biomass for Hydrogen and Biochar Production

Steam pyrolysis of woody biomass followed by catalytic steam reforming of pyrolysis vapors for renewable hydrogen production has been the center of attraction for many bench scale studies in recent years; however, sufficient pre-commercial testing has not been conducted or reported in literature. In addition, it is known that the cost of renewable hydrogen production could be reduced by co-production of biochar, a solid pyrolysis product used in carbon sequestration and soil enhancement for agriculture. This article presents results of a pilot-scale study for renewable hydrogen production from commercially available pine and peanut hull pellet biomass. In addition, the effect of temperature on biochar yield, pH, and its nutrient properties was also documented in bench-scale studies using pine chip, pine bark, hardwood, and peanut hull pellet biomass.

Bio-oil and bio-char production from corn cobs and stover by fast pyrolysis

Abstract Bio-oil and bio-char were produced from corn cobs and corn stover (stalks, leaves and husks) by fast pyrolysis using a pilot scale fluidized bed reactor. Yields of 60% (mass/mass) bio-oil (high heating values are ∼20 MJ kg −1 , and densities >1.0 Mg m −3 ) were realized from both corn cobs and from corn stover. The high energy density of bio-oil, ∼20–32 times on a per unit volume basis over the raw corn residues, offers potentially significant savings in transportation costs particularly for a distributed “farm scale” bio-refinery system. Bio-char yield was 18.9% and 17.0% (mass/mass) from corn cobs and corn stover, respectively. Deploying the bio-char co-product, which contains most of the nutrient minerals from the corn residues, as well as a significant amount of carbon, to the land can enhance soil quality, sequester carbon, and alleviate environmental problems associated with removal of crop residues from fields.