Methods to sequester and store atmospheric CO2 are critical to combat climate change. Alkaline-rich bioashes are potential carbon fixing materials. This work investigates potential co-benefits from mineralizing carbon in biomass ashes and partially replacing high embodied greenhouse gas (GHG) Portland cement (PC) in cement-based materials with these ashes. Specifically, rice hull ash (RHA), wheat straw ash (WSA), and sugarcane bagasse ash (SBA) were treated to mineralize carbon, and their experimental carbon content was compared to modeled potential carbonation. To understand changes in the cement-based storage materials, mortars made with CO2-treated WSA and RHA were experimentally compared to PC-only mortars and mortars made with ashes without prior CO2 treatment. Life cycle assessment methodology was applied to understand potential reductions in GHG emissions. The modeled carbonation was similar to 18 g-CO2/kg-RHA and similar to 180 g-CO2/kg-WSA. Ashes oxidized at 500 degrees C had the largest measured carbon content (5.4 g-carbon/kg-RHA and 35.3 g-carbon/kg-WSA). This carbon appeared to be predominantly residual from the biomass. Isothermal calorimetry showed RHA-PC pastes had similar heat of hydration to PC-pastes, while WSA-PC pastes exhibited an early (at similar to 1.5 min) endothermic dip. Mortars with 5 % and 15 % RHA replacement had 1-12 % higher compressive strength at 28 days than PC-only mortars, and milled WSA mortars with 5 % replacement had 3 % higher strength. A loss in strength was noted for the milled 15 % WSA, the CO2-treated 5 %, and the 15 % WSA mortars. Modeled reductions in GHG emissions from CO2-treated ashes were, however, marginal (<1 %) relative to the untreated ashes.

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Forests are a major natural resource of the state of California, where over a third of the land is forested, and provide a wide range of environmental, economic, and social benefits. Over the past decade, unprecedented drought, insect outbreaks and wildfires have resulted in large-scale tree mortality that greatly affects the forest ecosystem and poses significant threat to human health and welfare and to the environment. Forest thinning and management is considered imperative to improve forest health and resilience. Forest resources including dead and dying trees as well as the residues produced from forest thinning and timber harvesting operations could potentially be used to a greater degree than at present to generate electricity and other renewable energy to meet the increasing demand for more sustainable supplies and mitigate the risk of wildfires. However, efforts to construct new electricity generation capacity in the state at any scale over the last several decades have faced both economic and environmental challenges. As needs for alternative management approaches have become clear, opportunities have emerged for new bioenergy projects. These projects need to be effectively planned and potential economic and environmental performance carefully evaluated. Toward this purpose, an integrated framework model for lifecycle and technoeconomic assessment was developed to quantify environmental and economic impacts, initially for generating electricity using forest resources and with associated web services developed for an online application (forestdss.ucdavis.edu) that allows potential users to quickly estimate the economic and environmental performance of a potential facility at specified locations.

Biomass from specialty crops, including almonds, walnuts, and numerous others, serves as an important resource for energy and materials as agricultural systems evolve towards greater sustainability and circularity in management and operations. Biochar was produced from almond shells in a laboratory furnace at temperatures between 300 and 750 °C for residence times of 30 and 90 min with moisture contents of 5% to 15% wet basis. Response surface methodology was used to optimize the biochar yield. Feedstock and product temperatures were continuously monitored throughout the experiments. In addition, larger batches of biochar were also produced in a fixed-bed pilot-scale pyrolyzer. The yield of biochar was determined as a weight fraction of the amount of oven-dry almond shells used in each experiment. Physical and chemical characteristics of biochars were evaluated. Pyrolysis temperature and time were found to be the significant parameters affecting the biochar yield, with second-order regression models derived to fit yield results. As anticipated, highest biochar yields (65%) were obtained at a pyrolysis temperature of 300 °C and a pyrolysis time of 30 min due to the limited volatilization at this short residence at low temperature affecting torrefaction of the feedstock. The average biochar yield from the fixed-bed pilot-scale experiments was 39.5% and more closely aligned with the fixed carbon from standard proximate analyses. Higher pyrolysis temperatures resulted in higher C:N ratio and pH with the highest C:N ratio of 19:1 and pH of 10.0 obtained at a pyrolysis temperature of 750 °C for 90 min. Particle density increased with the increase of pyrolysis temperature. Results of this study can aid in predicting biochar yields from almond shells under different pyrolysis conditions and determining the amount of biochar required for different applications.

The geochemical signatures of a 12-year-old experimental bioreactor at a California landfill are used to identify elemental concentrations and ratios that characterize the landfill and relate it to the age and state of technology of the deposited waste. The bioreactor was constructed and sealed with a synthetic liner during 2001–2002 and operated and monitored as an anaerobic digester to enhance methane production. In 2013, the bioreactor was sampled and trace element concentrations of the extracted fine fractions were determined. The concentrations normalized to a regional soil composition, reveal systematic peaks for transition metals, alkali metals, heavy metals, and various metalloids and non-metals. A group of potential solder elements (Cu, Zn, Cd, In, Sn, Pb, Bi, and Sb) shows moderate to strong co-variations and is largely attributed to household electronic components and other similar products, while elements that correlated well with rare-earth and other elements are related to the diluting effect of a soil component used as cover. Batteries show modest to little effects on the overall concentrations. Circulating fluids (recycled leachate) in the controlled reactor did not completely redistribute and homogenize the elemental signatures within the time frame of the bioreactor. It is concluded that the present experimental landfill defines an Anthropocene marker identifiable by building material (plaster), PVC plastic, and household electronic components (Pb–Sn solder). These marker elements and ratios are variably diluted by soil components identified by alkali metals, rare-earths, and high field-strength elements (Hf, Zr, Nb, and Ta).

Polyhydroxyalkanoates (PHA) are a family of biodegradable plastics used as an ecofriendly alternative for conventional plastics in various applications. In this study, an industrial-scale PHA production system was designed and analyzed for the material flows and economics with the use of SuperPro Designer. Haloferax mediterranei was utilized to produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Byproduct streams from a local cheese plant, with an input of 168.7 metric ton/day (MT/day) lactose, were used as the feedstock. Three scenarios with different processes for the treatments of used enzyme and spent medium were investigated and the major factors that influence the overall economics were identified. The simulated system produces 9700 MT/year PHBV with a yield of 0.2 g PHBV/g lactose and an overall process efficiency of 87%. The breakeven price was found to be more sensitive to the lactose price than enzyme price. The scenario with enzyme reuse and spent medium recycling achieved the lowest breakeven price among others, which can be less than 4 $/kg PHA based on the delactosed permeate (DLP) unit price. The study suggests utilizing dairy derived feedstocks has the potential to make PHA competitive in the bioplastic market, which could be beneficial to both dairy and bioplastic industries.

Pretreatments are often needed for lignocellulosic biomass feedstocks before either thermochemical or biochemical conversion processes. Our previous research has demonstrated the potential of bioleaching, with its superior capability of removing certain inorganic compounds compared to water leaching, to improve biomass quality for thermochemical conversion in biofuel production. In this study, the bioleaching process was scaled up from 250 mL beakers to be carried out in custom-designed 2.5 L bioreactors. The fungus Aspergillus niger was used in the bioreactors for leaching sorghum straw biomass with an initial ash content of 6.0%. The effects of three operating parameters on leaching efficiency (i.e., residual ash content) were extensively studied, including the fungal mass added to each reactor, leaching time, and glucose concentration in the starting liquid phase. Response surface methodology (RSM) was used for the experiment design. The results showed that the average residual ash content of the sorghum feedstock after bioleaching was significantly lower (3.63 ± 0.19%) than that of the ash content (4.72 ± 0.13%) after water leaching (p < 0.00001). Among the three parameters, glucose concentration in the starting liquid phase had the most significant effect on leaching effectiveness (p = 0.0079). Based on this outcome, subsequent bioleaching experiments yielded reductions in residual ash content to as low as 2.73%.

Biogas consisting primarily of methane (CH4) and carbon dioxide (CO2) can be upgraded to a transportation fuel referred to as renewable natural gas (RNG) by removing CO2 and other impurities. RNG has energy content comparable to fossil compressed natural gas (CNG) but with lower life-cycle greenhouse gas (GHG) emissions. In this study, a light-duty cargo van was tested with CNG and two RNG blends on a chassis dynamometer in order to compare the toxicity of the resulting exhaust. Tests for reactive oxygen species (ROS), biomarker expressions (CYP1A1, IL8, COX-2), and mutagenicity (Ames) show that RNG exhaust has toxicity that is comparable or lower than CNG exhaust. Statistical analysis reveals associations between toxicity and tailpipe emissions of benzene, dibenzofuran, and dihydroperoxide dimethyl hexane (the last identification is considered tentative/uncertain). Further gas-phase toxicity may be associated with tailpipe emissions of formaldehyde, dimethyl sulfide, propene, and methyl ketene. CNG exhaust contained higher concentrations of these potentially toxic chemical constituents than RNG exhaust in all of the current tests. Photochemical aging of the vehicle exhaust did not alter these trends. These preliminary results suggest that RNG adoption may be a useful strategy to reduce the carbon intensity of transportation fuels without increasing the toxicity of the vehicle exhaust.

Escalating demands for infrastructure materials and energy worldwide necessitate exploration of means to efficiently utilize resources to support growing consumption. This work evaluates the potential symbiotic relationship between cultivation of an agricultural product (namely, rice), energy conversion, and utilization of bioash in the production of cement-based materials to improve the sustainability across multiple industries. Primarily, leaching methods of biomass that benefit energy conversion are evaluated as a means to simultaneously improve ash properties for use in cement-based materials. Specifically, this study considers water leaching and H3PO4 leaching of rice hulls and rice straw, which were subsequently ashed at three different temperatures, 600, 850, and 1100 degrees C. The effects of leaching on the ash characteristics, on the performance of ash-cement mortars, and on the greenhouse gas (GHG) emissions from both the mortars and energy produced are quantified. Findings showed that while acid leaching led to higher GHG emissions for electricity generation, leaching decreased concentrations of undesirable alkali metals and chlorides in the ash. Regardless of treatment and ashing temperature, the inclusion of bioash delayed the early strength development of the cement-based mortars. Yet, several permutations of treatment, feedstock type, and ashing temperature were found to contribute to the later-age strength development of cement-based materials while reducing related GHG emissions. Specifically, after 28 days of curing, mortars containing 15% cement replacement with unleached ash prepared at 600 degrees C had 1-5% lower compressive strength, and after 56 days, mortars with leached rice hull ash prepared at 600 degrees C had 5-6% lower compressive strengths. Further, the use of unleached and water-leached ashes in mortar led to reductions in GHG emissions up to 15%. Hence, this work shows that pretreatment methods applied to rice biomass residues may contribute to desirable cobenefits for energy and materials production.

Models of the shadows cast by orchard trees can provide useful information to assist in canopy and nutrient management, estimation of potential yield and water use. In this study, an analytical model was developed that calculates the shape, size, position and orientation of the shadows cast by the tree canopy and described the diurnal and seasonal changes in those shadows. The objective of this study was to derive analytical expressions to describe the positions and potential effects of shadows in time and space based on shape and size of the canopy, row and tree spacing, row orientation, and the latitude and the longitude of the orchard to compute canopy PAR interception considering the shading from neighbouring trees. The model was based on the assumption that canopies have spherical or ellipsoidal shape. Simulations were performed at different times of the day to study the shading patterns of trees and evaluated in terms of solar radiation received, transmitted and intercepted. The model was calibrated using field data to assist orchard design and canopy management based on lightbar scans obtained at different times of the day. The calibration procedure was tested on an almond orchard by comparing the shadows scanned and estimated by the model. The maximum average values between precision and recall were 87.50% and 87.75%, respectively. (c) 2020 IAgrE. Published by Elsevier Ltd. All rights reserved.

A small-scale, transportable membrane upgrading system designed to purify biogas was tested at two food waste digesters and one dairy digester. The system had a rated capacity of 100 Nm(3) h(-1) raw biogas making it suitable for the many small-scale biogas production facilities being developed across California. The membrane removed a majority of the carbon dioxide from the biogas with performance matching expected targets. The membrane system also removed trace levels of aldehydes, ketones, siloxanes, halocarbons, and sulfur-containing compounds from the biogas, mainly because the pre-cleaning steps removed these contaminants from the gas stream. The average composition of upgraded biomethane produced by the membrane system satisfied the trace contaminant requirements for pipeline injection in California. Residual air in the biogas was not removed efficiently by the membrane system which prevented methane concentrations from reaching levels sufficient to meet the heating value requirements for pipeline injection. Dedicated upgrading plants could carefully eliminate air leakage to address this issue, and/or mix propane into the biomethane to achieve the target heating value. An economic model developed for small scale biogas production facilities predicted that capital costs for a typical small-scale membrane separation plant exceed $2.46 million and projects only become financially viable over a 15 year return period when natural gas prices exceed $21.92 GJ(-1). Current market prices for petroleum natural gas are far below this level, and so financial incentives will be required to make small-scale biogas projects using membrane separation technology viable in the near term.

Biogas is a renewable energy source composed of methane, carbon dioxide, and other trace compounds produced from anaerobic digestion of organic matter. A variety of feedstocks can be combined with different digestion techniques that each yields biogas with different trace compositions. California is expanding biogas production systems to help meet greenhouse gas reduction goals. Here, we report the composition of six California biogas streams from three different feedstocks (dairy manure, food waste, and municipal solid waste). The chemical and biological composition of raw biogas is reported, and the toxicity of combusted biogas is tested under fresh and photochemically aged conditions. Results show that municipal waste biogas contained elevated levels of chemicals associated with volatile chemical products such as aromatic hydrocarbons, siloxanes, and certain halogenated hydrocarbons. Food waste biogas contained elevated levels of sulfur-containing compounds including hydrogen sulfide, mercaptans, and sulfur dioxide. Biogas produced from dairy manure generally had lower concentrations of trace chemicals, but the combustion products had slightly higher toxicity response compared to the other feedstocks. Atmospheric aging performed in a photochemical smog chamber did not strongly change the toxicity (oxidative capacity or mutagenicity) of biogas combustion exhaust.

Agricultural residues and energy crops often contain high contents of alkali metals, chlorine, silica, and other elements that promote slagging, fouling, corrosion, and gas emission during thermochemical conversion (e.g., combustion and gasification). Water leaching is a common method, but not always effective to reduce such elements. Bioleaching by adding microbes to water leaching was introduced to leach cellulosic biomass in this study. Three microbial species including two fungi (Fusarium oxysporum and Aspergillus niger) and one bacterium (Burkholderia fungorum) were selected to leach four lignocellulosic feedstocks such as corn stover, wheat straw, switchgrass, and sorghum. Among three microbes, A. niger was found the most efficient to remove most elements by 80% in 48 h, and sorghum was relatively more amenable to bioleaching. With A. niger, the bioleaching with water to feedstock (w/w) ratio of 25 for 6 h was sufficient to leach K (85%), Cl (90%), Mg (60%), and P (70%) from sorghum. Overall, bioleaching is more efficient than water leaching except for Na. Studies on bioleaching mechanism indicated that the acidification resulted from organic acids produced by A. niger during bioleaching might contribute to the higher leaching efficiency over other microbial species and water leaching.

This experimental and numerical study investigates the effect of flow field alteration via bluff body flow disturbers in the packed bed Fischer-Tropsch (FT) reaction, which is known to be limited by heat and mass transfer and chemical kinetics as prescribed by the reactor geometry, flow and temperature fields, and catalyst properties. Experiments were carried out using a 188 cm(3) reactor with 30.8 aspect (length-to-diameter) ratios loaded with 20% cobalt/Al2O3 catalyst and controlled at 200 degrees C at the exterior wall. Numerical simulation was carried out in the commercial ANSYS Fluent package. Experimental results show that the bluff bodies increased the CO (carbon monoxide) conversion and C7+ yields (hydrocarbons with 7 carbon chains or longer) across the factorial design space by as much as 1.8x and 3.3x of the baseline values, respectively. Numerical simulations suggest that these increases can be attributed to higher thermal conductivities and local velocities for greater heat rejection and lower external mass transfer resistance, respectively. Results suggest that the use of internal flow disturbers in the packed bed had significant influence in lowering the heat and mass transfer resistances of the FT process, and can improve the cost-competitiveness of FT liquids production in the small scale.

This chapter contains sections titled: Nomenclature Introduction Combustion Systems Fundamentals of Biomass Combustion Pollutant Emissions and Environmental Impacts References

Experiments were performed on a laboratory scale fluidized bed gasifier to characterize the gasification products of almond shell and hull removed in nut processing operations and to determine the effect of gasifying media on bed agglomeration. The higher heating value of syngas during air gasification of almond biomass ranged from 4 to 6 MJ m(-3) while gas concentrations ranged from 14 to 18% H-2, 3-4% CH4, 43-50% N-2, 16-19% CO, and 16-17% CO2. For steam gasification, higher heating value was 10-12 MJ m(-3) and gas concentrations were 35-40% H-2, 5-7% CH4, 17-21% N-2, 18-21% CO, and 16-18% CO2. The high level of potassium in the almond shells led to strong corrosion and bed agglomeration due to flue gas transport of potassium compounds. These resulting pervasive kalsilite reactions were significantly worse under air gasification than under steam gasification. As a result of prolonged duration and elevated temperature approaching 1,000 degrees C, the corrosinal reaction changes to formation of an adhesive potassium distillate melt locally forming strong bonds. This latter is interpreted as a result of aerosol transported of melt particles.

Hybrid poplar has potential as feedstock for the production of bioenergy and bio-based products. Planning effective placement of hybrid poplar based biorefinery facilities takes tremendous time and financial resources. A hybrid poplar based biorefinery siting application (HP-BiSWA), a web-enabled refinery siting application, was developed so that potential stakeholders may quickly assess available resources at selected locations and provide information relating to the economic competitiveness and financial risks associated with construction and operation. At present, the tool supports evaluation of the potential for hybrid poplar based jet fuel and acetic acid production based on user-specified conditions. The application is generally expandable to other feedstock, technology, and product types. HP-BiSWA uses various modules (i.e. 3PG-crop growth model and farm budget application) and services (i.e. parcel service, transportation routing service, crop service, soil and weather services) to retrieve and estimate information to optimize and select potential parcels for poplar cultivation, and ultimately determine net revenue for biofuel production under selected decision options. To demonstrate the utility of HP-BiSWA, a case study analysis was performed for Centralia, WA based on a 380 ML/yr (100 MGY) jet fuel biorefinery using two scenarios: (1) a 175 km feedstock supply radius with 50% pastureland use, and (2) a 225 km feedstock supply radius with 25% pastureland use. The case study captures the interactive effects on biorefinery performance with changes in feedstock supply area and available water, power, and other resources for operation of the biorefinery.

An economic linear programming model with a sliding time window was developed to assess designing and scheduling a biomass-fueled combined heat and power system consisting of biomass gasifier, internal combustion engine, heat recovery set, heat-only boiler, producer gas storage and thermal energy storage. A case study was examined for a conceptual utility grid-connected BCHP application in Davis, California under different scenarios. The results show that a 100 kW biomass gasifier and engine combination with energy storage was the most cost effective design based on the assumed energy load profile, utility tariff structure and technical and finical performance of the system components. Engine partial load performance was taken into consideration. Sensitivity analyses demonstrate how the optimal BCHP configuration changes with varying demands and utility tariff rates. (C) 2018 Elsevier Ltd. All rights reserved.

A load shifting algorithm based on economic linear programming with model predictive control was developed to minimize the operating cost of a biomass combined heat and power based microgrid system. The model simultaneously manages supply and demand of both electrical and thermal energy as decision variables. An algorithm was developed to optimize the shifting of loads based on the renewable energy generation and time-of-use tariff. As an illustrative example, a case study was examined for a conceptual utility grid-connected microgrid application in Davis, California. For the assumptions used, the proposed load shifting algorithm improved the performance of the microgrid by changing the load pattern and reduced the operating cost by 6.06% and increased the renewable energy fraction by 6.34% compared with the conventional no-load shift case. Monte Carlo simulation was used to evaluate uncertainties among the renewable energy, demand side, and economic assumptions, generating a probability density function for the cost of energy.

White poplar is an important biomass resource because of its high yield and fast-growing characteristics. Experiments were conducted to study the effects of microwave power, moisture content, and particle size on the heating rate and biochar yield. A Central Composite Design (CCD) was used to optimize the biochar yield. The CCD results showed that a maximum temperature-increasing rate of 2.71 degrees C/s was obtained with a microwave power of 2 kW and a small particle size of 100-mesh. High power, small size, and high moisture content would benefit the increase of the heating rate. An optimum biochar yield of 0.905 kg per kg poplar was obtained with a microwave power of 3 kW, moisture content of 1%, and temperature of 500 degrees C.