David Bransby

How biotech can transform biofuels

For cellulosic ethanol to become a reality, biotechnological solutions should focus on optimizing the conversion of biomass to sugars.

A review of carbon and nitrogen balances in switchgrass grown for energy

Abstract Increased atmospheric CO2, caused partly by burning fossil fuels, is assumed to elevate the risk of global warming, while nitrate contamination of surface runoff and groundwater from fertilizer and agricultural wastes constitutes a serious environmental hazard on a regional scale. Switchgrass (Panicum virgatum L.) grown as an energy crop could reduce atmospheric CO2 accumulation by replacing fossil fuels and sequestering C. It could also improve soil productivity by C sequestration, and reduce NO−13 contamination of water by absorbing N lost from fertilizer and agricultural waste if planted in filter strips on adjacent land. The objective of this study was to assess potential impacts of switchgrass on C and N balances by reviewing and synthesizing information from current literature, unpublished data and on-going research. Replacing fossil fuels with switchgrass, or any other biomass, will have a much greater effect on atmospheric CO2 than C sequestration. This is because replacing fossil fuels provides a cumulative effect, while C sequestration offers only a one-time benefit. Furthermore, switchgrass will provide net gains in C sequestration only if it replaces annual row crops, but not if it replaces grazed pasture. Nitrogen recovery by switchgrass in an Alabama study was 65.6%, which compares favorably with the 50% recovery frequently quoted as the norm for wheat (Triticum aestivum L.) and corn (Zea mays L).

Impact of row spacing, nitrogen rate, and time on carbon partitioning of switchgrass

Cultivation of switchgrass (Panicum virgatum L.) as an energy crop could lower atmospheric carbon dioxide (CO2) levels by replacing fossil fuel and sequestering carbon (C). Information on the details of C partitioning within the switchgrass–soil system is important in order to quantify how much C is sequestered in switchgrass shoots, roots, and soil. No studies of C partitioning in a switchgrass–soil system under field conditions have been conducted. This study was aimed at determining the impact of agricultural management practices, such as row spacing and nitrogen (N) application rate, on C partitioning within the switchgrass–soil system; changes in C partitioning with time after switchgrass establishment were also considered. The results indicate that C storage in switchgrass shoots was higher with wide than narrow rows, and increased with N application rates. These responses were due to higher yields with wide than narrow rows and higher yields as N application rate increased. Carbon storage in shoots was 14.4% higher with 80-cm than 20-cm row spacing. Annual application of increased C storage in shoots by 207% and 27% when compared with annual applications of 0 and , respectively. Carbon storage increased by 62% over time from 1995 to 1996 in newly established switchgrass on sandy loam soil in the coastal plain of Alabama. Rate of C increase in roots (72%) was higher than in shoots (49%) between 1995 and 1996. Carbon storage was in order of soil C > root C > shoot C in both 1995 and 1996. The root/shoot ratio of C storage was 2.2. It appears that C partitioning to roots plays an important role in C sequestration by switchgrass.

Switchgrass cofiring: pilot scale and field evaluation.

Abstract A study is under way to evaluate the feasibility, costs, and benefits of co-milling and direct injection cofiring of switchgrass with coal as a potential renewable energy source. Switchgrass is an American native prairie grass, ideally adapted to the eastern United States. The grass is highly productive, requires little fertilization and herbicide, and can be grown on marginal land. There are four phases in the study, which look at (1) farm production issues, (2) pilot co-milling, (3) pilot combustion tests, and (4) full-scale demonstration. To date, good data have been obtained on farm production costs and field processing and handling issues. Pilot-scale milling tests and combustion tests of blends of switchgrass with coal have been successfully completed, and a full-scale demonstration of direct pneumatic injection of switchgrass for co-firing in a pulverized coal boiler is planned for the spring of 2001.

Effects of grazing management practices on parasite load and weight gain of beef cattle.

Stocking rate, method of grazing (rotational vs. continuous) and supplementation are three grazing management variables which strongly affect weight gain of beef cattle. However, reports on the interaction between these variables and parasitism in beef cattle are often conflicting or not conclusive. Although several studies have shown increased parasite loads with increased stocking rates, few studies have included animals treated and untreated with anthelmintics at several stocking rates. Those that did have this treatment combination did not show greater response in weight gain to treatment with anthelmintics at high stocking rates than at low stocking rates. Experiments designed to investigate the effect of rotational and continuous grazing on parasitism have provided variable results. However, as the high stock densities associated with rotational grazing will probably cause animals to graze closer to the ground and to dung pats, and to spread dung more with their hooves, it is not likely that rotational grazing will reduce the need for chemotherapy. Some studies have shown reduced parasite loads with supplementation of untreated animals, but none has apparently investigated whether weight gain response to treatment with anthelmintics is greater for non-supplemented animals than for supplemented animals. Published studies on the interaction between management factors and parasitism in grazing animals reveal many weaknesses. Elimination of these weaknesses and cognisance of recent trends in design and conduct of grazing experiments will substantially improve the quality and value of research in this field.

Biomass yield and composition, and winter survival of tall grasses in Alabama

The objectives of this study were to determine yield and composition of tall grasses grown in central Alabama and to determine winter survival and emergence of napiergrass and energycane planted in autumn at three depths in central and northern Alabama. Plots for the first experiment were established during summer, 1986, and were harvested every autumn thereafter for four years. Samples of napiergrass and energycane taken in 1990 were analyzed for nitrogen and several fiber components. Total yields varied among years, which differed in both moisture and temperature conditions. Yields ranged from 15.9 to 32.4 Mg ha−1 for energycane, 4.5 to 30.4 Mg ha−1 for N-51 napiergrass and from 1.4 to 22.2 Mg ha−1 for PI 300086 napiergrass. Sugarcane and sorghum yields ranged from 0 to 8.9 and 1.8 to 11.7 Mg ha−, respectively. Variation in dry matter composition was low, although N concentration of energycane was significantly lower than that of both napiergrass entries. The second experiment indicated that winter survival and spring shoot emergence from stalks planted in autumn appeared best at a 10-cm planting depth for all entries.

Extraction of hyperoside and quercitrin from mimosa (Albizia julibrissin) foliage

Mimosa, an excellent energy crop candidate because of its high growth yield, also contains, on a dry basis, 0.83% hyperoside and 0.90% quercitrin. Hyperoside has been documented as having anti-inflammatory and diurectic properties, whereas quercitrin may play a role in intestinal repair following chronic mucosal injury. Thus, mimosa might first be extracted for important antioxidant compounds and then used as a feedstock for energy production. This article presents results from studies aimed at determining the effect of three extraction parameters (temperature, solvent composition, and time) on the yield of these important quercetin compounds. Conditions are sought which maximize yield and concentration, whereas complementing subsequent biomass pretreatment, hydrolysis and fermentation.

Engineering Advantages, Challenges and Status of Grass Energy Crops

High yield with low inputs, resistance to disease, pests and drought, adaptation to a wide range of soils and climates, and biomass composition that is optimized for end use are identified as important traits for cellulosic biomass crops. Current status and future prospects for genetic improvement are reviewed for grass crops, using Miscanthus, switchgrass, sugarcane (or energy cane) and sorghum as examples. In addition, possible approaches for integrating grasses into cellulosic biomass supply systems are discussed. It is concluded that both perennial and annual grasses can play a significant role in providing cellulosic biomass for a wide range of bioenergy applications, and considerable potential exists for genetic improvement of grass crops for this purpose.

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small‐scale and short‐term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long‐term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field‐scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm‐scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM‐ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country.