Akwasi A. Boateng

Biochar: A Synthesis of Its Agronomic Impact beyond Carbon Sequestration

Biochar has been heralded as an amendment to revitalize degraded soils, improve soil carbon sequestration, increase agronomic productivity, and enter into future carbon trading markets. However, scientific and economic technicalties may limit the ability of biochar to consistently deliver on these expectations. Past research has demonstrated that biochar is part of the black carbon continuum with variable properties due to the net result of production (e.g., feedstock and pyrolysis conditions) and postproduction factors (storage or activation). Therefore, biochar is not a single entity but rather spans a wide range of black carbon forms. Biochar is black carbon, but not all black carbon is biochar. Agronomic benefits arising from biochar additions to degraded soils have been emphasized, but negligible and negative agronomic effects have also been reported. Fifty percent of the reviewed studies reported yield increases after black carbon or biochar additions, with the remainder of the studies reporting alarming decreases to no significant differences. Hardwood biochar (black carbon) produced by traditional methods (kilns or soil pits) possessed the most consistent yield increases when added to soils. The universality of this conclusion requires further evaluation due to the highly skewed feedstock preferences within existing studies. With global population expanding while the amount of arable land remains limited, restoring soil quality to nonproductive soils could be key to meeting future global food production, food security, and energy supplies; biochar may play a role in this endeavor. Biochar economics are often marginally viable and are tightly tied to the assumed duration of agronomic benefits. Further research is needed to determine the conditions under which biochar can provide economic and agronomic benefits and to elucidate the fundamental mechanisms responsible for these benefits.

Switchgrass as a biofuels feedstock in the USA.

Switchgrass (Panicum virgatum L.) has been identified as a model herbaceous energy crop for the USA. In this review, we selectively highlight current USDA-ARS research on switchgrass for biomass energy. Intensive research on switchgrass as a biomass feedstock in the 1990s greatly improved our understanding of the adaptation of switchgrass cultivars, production practices, and environmental benefits. Several constraints still remain in terms of economic production of switchgrass for biomass feedstock including reliable establishment practices to ensure productive stands in the seeding year, efficient use of fertilizers, and more efficient methods to convert lignocellulose to biofuels. Overcoming the biological constraints will require genetic enhancement, molecular biology, and plant breeding efforts to improve switchgrass cultivars. New genomic resources will aid in developing molecular markers, and should allow for marker-assisted selection of improved germplasm. Research is also needed on profitable mana...

Guaiacol Hydrodeoxygenation Mechanism on Pt(111): Insights from Density Functional Theory and Linear Free Energy Relations

Density functional theory is used to study the adsorption of guaiacol and its initial hydrodeoxygenation (HDO) reactions on Pt(111). Previous Brønsted-Evans-Polanyi (BEP) correlations for small open-chain molecules are inadequate in estimating the reaction barriers of phenolic compounds except for the side group (methoxy) carbon-dehydrogenation. New BEP relations are established using a select group of phenolic compounds. These relations are applied to construct a potential-energy surface of guaiacol-HDO to catechol. Analysis shows that catechol is mainly produced via dehydrogenation of the methoxy functional group followed by the CHx (x<3) removal of the functional group and hydrogenation of the ring carbon, in contrast to a hypothesis of a direct demethylation path. Dehydroxylation and demethoxylation are slow, implying that phenol is likely produced from catechol but not through its direct dehydroxylation followed by aromatic carbon-ring hydrogenation.

Mass Balance, Energy, and Exergy Analysis of Bio-Oil Production by Fast Pyrolysis

Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture (USDA). USDA is an equal opportunity provider and employer. Mass, energy, and exergy balances are analyzed for bio-oil production in a bench-scale fast pyrolysis system developed by the USDA’s Agricultural Research Service (ARS) for the processing of commodity crops to fuel intermediates. Because mass balance closure is difficult to achieve due, in part, to the system’s small size and complexity a linear programming optimization model is developed to improve closure of elemental balances without losing the overall representation of the pyrolysis products. The model results provide an opportunity to analyze true energy and exergy balances for the system. While energy comparisons are based on heating values, exergy flows are computed using statistical relationships and other standard techniques. Comparisons were made for a variety of biomass feedstocks including energy crops and various byproducts of agriculture and bioenergy industry. The mass model allows for proper accounting of sources of mass loss and suggestions for improved system performance. Energy recovery and exergetic efficiency are compared for a variety of pyrolysis product utilization scenarios including use of biochar and noncondensable gases as heat sources. Exergetic efficiencies show high potential for energy utilization when all the pyrolysis product streams can be recycled to recuperate their internal energy. The exergy analysis can be beneficial to developing exergetic life cycle assessments (ELCA) for the fast pyrolysis process as sustainable technology for advanced biofuels production.

Overexpression of SbMyb60 impacts phenylpropanoid biosynthesis and alters secondary cell wall composition in Sorghum bicolor.

The phenylpropanoid biosynthetic pathway that generates lignin subunits represents a significant target for altering the abundance and composition of lignin. The global regulators of phenylpropanoid metabolism may include MYB transcription factors, whose expression levels have been correlated with changes in secondary cell wall composition and the levels of several other aromatic compounds, including anthocyanins and flavonoids. While transcription factors correlated with downregulation of the phenylpropanoid biosynthesis pathway have been identified in several grass species, few transcription factors linked to activation of this pathway have been identified in C4 grasses, some of which are being developed as dedicated bioenergy feedstocks. In this study we investigated the role of SbMyb60 in lignin biosynthesis in sorghum (Sorghum bicolor), which is a drought-tolerant, high-yielding biomass crop. Ectopic expression of this transcription factor in sorghum was associated with higher expression levels of genes involved in monolignol biosynthesis, and led to higher abundances of syringyl lignin, significant compositional changes to the lignin polymer and increased lignin concentration in biomass. Moreover, transgenic plants constitutively overexpressing SbMyb60 also displayed ectopic lignification in leaf midribs and elevated concentrations of soluble phenolic compounds in biomass. Results indicate that overexpression of SbMyb60 is associated with activation of monolignol biosynthesis in sorghum. SbMyb60 represents a target for modification of plant cell wall composition, with the potential to improve biomass for renewable uses.

Reliable Peak Selection for Multisample Analysis with Comprehensive Two-Dimensional Chromatography

Comprehensive two-dimensional chromatography is a powerful technology for analyzing the patterns of constituent compounds in complex samples, but matching chromatographic features for comparative analysis across large sample sets is difficult. Various methods have been described for pairwise peak matching between two chromatograms, but the peaks indicated by these pairwise matches commonly are incomplete or inconsistent across many chromatograms. This paper describes a new, automated method for postprocessing the results of pairwise peak matching to address incomplete and inconsistent peak matches and thereby select chromatographic peaks that reliably correspond across many chromatograms. Reliably corresponding peaks can be used both for directly comparing relative compositions across large numbers of samples and for aligning chromatographic data for comprehensive comparative analyses. To select reliable features for a set of chromatograms, the Consistent Cliques Method (CCM) represents all peaks from all chromatograms and all pairwise peak matches in a graph, finds the maximal cliques, and then combines cliques with shared peaks to extract reliable features. The parameters of CCM are the minimum number of chromatograms with complete pairwise peak matches and the desired number of reliable peaks. A particular threshold for the minimum number of chromatograms with complete pairwise matches ensures that there are no conflicts among the pairwise matches for reliable peaks. Experimental results with samples of complex bio-oils analyzed by comprehensive two-dimensional gas chromatography (GCxGC) coupled with mass spectrometry (GCxGC-MS) indicate that CCM provides a good foundation for comparative analysis of complex chemical mixtures.

Aspen Plus® and economic modeling of equine waste utilization for localized hot water heating via fast pyrolysis.

Aspen Plus(®) based simulation models have been developed to design a pyrolysis process for on-site production and utilization of pyrolysis oil from equine waste at the Equine Rehabilitation Center at Morrisville State College (MSC). The results indicate that utilization of all the available waste from the sites 41 horses requires a 6 oven dry metric ton per day (ODMTPD) pyrolysis system but it will require a 15 ODMTPD system for waste generated by an additional 150 horses at the expanded area including the College and its vicinity. For this a dual fluidized bed combustion reduction integrated pyrolysis system (CRIPS) developed at USDAs Agricultural Research Service (ARS) was identified as the technology of choice for pyrolysis oil production. The Aspen Plus(®) model was further used to consider the combustion of the produced pyrolysis oil (bio-oil) in the existing boilers that generate hot water for space heating at the Equine Center. The model results show the potential for both the equine facility and the College to displace diesel fuel (fossil) with renewable pyrolysis oil and alleviate a costly waste disposal problem. We predict that all the heat required to operate the pyrolyzer could be supplied by non-condensable gas and about 40% of the biochar co-produced with bio-oil. Techno-economic Analysis shows neither design is economical at current market conditions; however the 15 ODMTPD CRIPS design would break even when diesel prices reach

Pelletized Biochar as a Carrier for AM Fungi in the On-Farm System of Inoculum Production in Compost and Vermiculite Mixtures

11.40/gal. This can be further improved to

Coke Produced from Lower-Oxygen Fast-Pyrolysis Oil, A New Approach to Produce Renewable Anode Raw Materials

7.50/gal if the design capacity is maintained at 6 ODMTPD but operated at 4950 h per annum.

Effect of biochar soil-amendments on Allium porrum growth and arbuscular mycorrhizal fungus colonization

ABSTRACT. On farm production of arbuscular mycorrhizal (AM) fungi is suitable for vegetable and horticultural crop production because the inocula may be efficiently mixed into horticultural potting media for plant production in the greenhouse. These inocula are not amenable for use in row crop production because they are not in a form suitable for mechanical application. Experiments were conducted in which light expanded clay aggregates (LECA) and pelletized biochar were used in the media for the on-farm production of AM fungus inoculum utilizing compost and vermiculite with Paspalum notatum Flugge as the nurse host plant. Subsequent colonization assays using P. notatum failed to detect any infectivity of LECA granules, indicating that the AM fungi did not infest the granules. However, as little as 0.1 g fresh wt of biochar was sufficient to produce colonization of test plants. Biochar pellets recovered from the on-farm system used to propagate Rhizophagus intraradices exhibited 24 propagules g−1 fresh wt. These results indicate the promise of pelletized biochar as a carrier for AM fungi in inoculum production systems.