Effect of waste organic amendments on Populus sp biomass production and thermal characteristics

Energy crops and thermal conversion of the obtained biomass is a feasible route for the production of energy. In this work, dehydrated composted sewage sludge (BIOSOLIDS) and sludge from dairy wastewater treatment (MUD) were used as organic amendments on four different poplar clones (UNAL, I-214, AF-2 and AF-8) and. These amendments were yearly applied throughout a four years' study aiming to find out the effects on both agronomic (diameter, height and biomass volume of the trees) and thermal (fuel and thermogravimetric analysis) properties of the poplars. The application of MUD improved the agronomic characteristics of the poplars, especially those of UNAL and AF-2. Thermal results were not as conclusive, but pointed to an improvement of the thermal behavior of UNAL under BIOSOLIDS treatment and of AF-2 and AF-8 under MUD fertilization. On the whole, the most favorable case was that of the AF-2 under fertilization with MUD.     

Pilot-scale high solids thermophilic anaerobic digestion of municipal solid waste with an emphasis on nutrient requirements

A pilot study was conducted to assess the biodegradable organic fraction of municipal solid waste (BOF/MSW) as a substrate in a high-solids anaerobic digestion process. Results obtained indicate that a typical BOF/MSW in the United States is deficient in most macro and micro-nutrients required for robust and stable digestion. The BOF/MSW was supplemented with nutrient-rich organic wastes such as wastewater treatment plant sludges, dairy manure, and synthetic chemical solutions to correct nutritional deficiencies. The combined addition of wastewater treatment plant sludge and dairy manure to a typical BOF/MSW significantly elevated the gas production rate and enhanced the process stability. Microbial nutrient requirements are identified and nutrient concentrations for stable operation are quantified.     

Integrating livestock manure with a corn–soybean bioenergy cropping system improves short-term carbon sequestration rates and net global warming potential

Carbon cycling and the global warming potential (GWP) of bioenergy cropping systems with complete biomass removal are of agronomic and environmental concern. Corn growers who plan to remove corn stover as a feedstock for the emerging cellulosic ethanol industry will benefit from carbon amendments such as manure and compost, to replace carbon removed with the corn stover. The objective of this research was to determine the effect of beef cattle feedlot manure and composted dairy manure on short-term carbon sequestration rates and net global warming potential (GWP) in a corn–soybean rotation with complete corn-stover removal. Field experiments consisting of a corn–soybean rotation with whole-plant corn harvest, were conducted near East Lansing, MI over a three-year period beginning in 2002. Compost and manure amendments raised soil carbon (C) at a level sufficient to overcome the C debt associated with manure production, manure collection and storage, land application, and post-application field emissions. The net GWP in carbon dioxide equivalents for the manure and compost amended cropping systems was ?934 and ?784 g m^?2 y^?1, respectively, compared to 52 g m^?2 y^?1 for the non-manure amended synthetic fertilizer check. This work further substantiates the environmental benefits associated with renewable fuels and demonstrates that with proper management, the integration of livestock manures in biofuel cropping systems can enhance greenhouse gas (GHG) remediation.     

Nitrogen fertilization of switchgrass increases biomass yield and improves net greenhouse gas balance in northern Michigan, U.S.A

Nitrogen (N) fertilization can increase bioenergy crop production; however, fertilizer production and application can contribute to greenhouse gas (GHG) emissions, potentially undermining the GHG benefits of bioenergy crops. The objective of this study was to evaluate the effects of N fertilization on GHG emissions and biomass production of switchgrass bioenergy crop, in northern Michigan. Nitrogen fertilization treatments included 0 kg ha⁻¹ (control), 56 kg ha⁻¹ (low) and 112 kg ha⁻¹ (high) of N applied as urea. Soil fluxes of CO₂, N₂O and CH₄ were measured every two weeks using static chambers. Indirect GHG emissions associated with field activities, manufacturing and transport of fertilizer and pesticides were derived from the literature. Switchgrass aboveground biomass yield was evaluated at the end of the growing season. Nitrogen fertilization contributed little to soil GHG emissions; relative to the control, there were additional global warming potential of 0.7 Mg ha⁻¹ y⁻¹ and 1.5 Mg ha⁻¹ y⁻¹ as CO₂ equivalents (CO₂eq), calculated using the IPCC values, in the low and high N fertilization treatments, respectively. However, N fertilization greatly stimulated CO₂ uptake by switchgrass, resulting in 1.5- and 2.5-fold increases in biomass yield in the low and high N fertilization treatments, respectively. Nitrogen amendments improved the net GHG benefits by 2.6 Mg ha⁻¹ y⁻¹ and 9.4 Mg ha⁻¹ y⁻¹ as CO₂eq relative to the control. Results suggest that N fertilization of switchgrass in this region could reduce (15-50%) the land base needed for bioenergy production and decrease pressure on land for food and forage crop production.     

What is the potential for biogas digesters to improve soil fertility and crop production in Sub-Saharan Africa?

Three alternative soil amendments of organic wastes are considered: application of untreated animal manures, bioslurry from biogas digestion, composted materials, and biochar produced by pyrolysis cook-stoves. Application of untreated manures provides high input of available nutrients, which results in an initial flush in crop growth. However, risks of losing nutrients are high because manure is usually applied before sowing to avoid reduced yields due to phytotoxicity, resulting in increased losses by leaching or volatilization. Furthermore, the heterogeneous nature of untreated manures results in immobilization of nutrients by carbon-rich materials. A greater amount of nutrients are potentially available to crops from applied bioslurry. Typically 5–10% of the nitrogen is lost during anaerobic digestion, but bioslurry provides immediately available nutrients that can be applied as needed, so reducing risks of nutrient loss. If, however, bioslurry was applied in a single dose, losses would be similar in magnitude to untreated manures. Risks of nutrient losses are also lower when wastes are applied as composts, but in contrast to bioslurry, this is because the concentration of immediately available nutrients is very low, most nutrients being held in organic form that will become available only slowly over the growing season. Composts provide an option for single dose application, but a larger proportion of nitrogen is lost during composting (26–51%) than during anaerobic digestion (5–10%). Losses of nitrogen during pyrolysis are also very high (70–90%), but biochar can reduce losses of native soil nutrients by providing exchange sites that hold nutrients in the soil.     

Efficacies of inocula on the startup of anaerobic reactors treating dairy manure under stirred and unstirred conditions

Inocula play an important role in anaerobic reactor startup by balancing the populations of Syntrophobacter and methanogens. Such balances make syntrophic metabolism thermodynamically feasible in anaerobic digestion. In this study, the effect of inocula on the performance of dairy manure digestion was investigated by analyzing the change in volatile fatty acids (VFA), total solids (TS), volatile solids (VS), specific biogas production (SGPR), and specific methane production (SPMP) as well as scanning and transmission electron micrographs. The study was performed at four treatments. Treatment one was granular sludge (GM); treatment two was non-granular sludge (SM); treatment three was mixed culture from an anaerobic lagoon (LM); while the fourth treatment (the control denoted MM) did not receive any exogenous inocula. In addition, stirred and unstirred conditions were maintained in the reactors to determine their effect on reactor startup. Performance ranking based on the SGPR and SPMP of treatments (in descending order) was: GM, SM, LM and MM under stirred conditions. Under unstirred conditions, performance ranking (also in descending order) was: SM, GM, LM, and MM. Results of the examination of microcolonies in the granular, non-granular sludge, and dairy manure suggest that syntrophic juxtaposition of methanogens and Syntrophobacter in granular inoculum was common while it was less visible in non-granular sludge, and completely absent in dairy manure.     

Energizing marginal soils – The establishment of the energy crop Sida hermaphrodita as dependent on digestate fertilization,NPK, and legume intercropping

Growing energy crops in marginal, nutrient-deficient soils is a more sustainable alternative to conventional cultivation. The use of energy-intensive synthetic fertilizers needs to be reduced, preferably via closed nutrient loops in the biomass production cycle. In the present study based on the first growing season of a mesocosm experiment using large bins outdoors, we evaluated the potential of the energy plant Sida hermaphrodita to grow in a marginal sandy soil. We applied different fertilization treatments using either digestate from biogas production or a commercial mineral NPK-fertilizer. To further increase independence from synthetically produced N-fertilizers, the legume plant Medicago sativa was intercropped to introduce atmospherically fixed nitrogen and potentially facilitate the production of additional S. hermaphrodita biomass. We found digestate to be the best performing fertilizer because it produced similar yields as the NPK fertilization but minimized nitrate leaching. Legume intercropping increased the total biomass yield by more than 100% compared to S. hermaphrodita single cropping in the fertilized variants. However, it negatively influenced the performance of S. hermaphrodita in the following year. We conclude that a successful establishment of S. hermaphrodita for biomass production in marginal soils is possible and digestate application formed the best fertilization method when considering a range of aspects including overall yield, nitrate leaching, nitrogen fixation of M. sativa, and sustainability over time.     

Anaerobic membrane bioreactors and the influence of space velocity and biomass concentration on methane production for liquid dairy manure

Two pilot-scale anaerobic membrane bioreactors (AnMBRs) and a control completely mixed digester (CMD) were constructed to evaluate the influence of space velocity and biomass concentration on methane production for sand separated dairy manure. A negative impact on methane production resulted with operating the AnMBR system at 972 μHz–2960 μHz but no impact was found when operating at 69 μHz and 312 μHz. Operating at 69 μHz–350 μHz is realistic for a field installation. Despite the higher biomass concentration, the methane production of the AnMBRs was nearly equal to the CMD. An AnMBR with 69 μHz was operated equivalent to a CMD by returning all permeate to the digester tank and removing excess biomass directly from the reactor tank resulting in a hydraulic retention time (HRT) equal to the solids retention time (SRT). When using sand separated dairy manure and an HRT (and equal SRT) of 12 d, both systems produced methane at an equal rate, suggesting that the pump/membrane system did not influence methane production. The most likely reason was mass transfer limitations of hydrolytic enzymes. Based on methane production and volatile fatty acids analysis, it appears the fermentable substrate available for degradation was similar. The AnMBR proved to have benefit as part of an integrated nutrient management system that produced water that is virtually free of particulate nutrients, especially phosphorus. This enables the irrigation of the water to crops that need nitrogen and the efficient movement of phosphorus, as a solid, to needed locations.     

Biomass production and soil nutrients in organic and inorganic fertilized willow biomass production systems

The use of organic waste materials as nutrient sources for willow biomass production is an attractive means to decrease fertilization costs, increase biomass production and reduce greenhouse gas emissions associated with the system. In this study, changes in soil nutrients and biomass production of two willow varieties (Salix miyabeana–SX64 and Salix purpurea–9882-34) in organic and synthetic fertilized systems were compared at three locations in Northeastern U.S.A: Middlebury VT (MID), Delhi NY (DEL) and Fredonia NY (FRE). A 150 and 200 kg available N ha⁻¹ of urea as commercial fertilizer (CF), biosolid compost (BC) and digested dairy manure (DM) and a control (CT0) treatments were applied in June 2008 to the willow which was re-sprouting after coppice. There was no significant difference (p > 0.05) in biomass production among the fertilization treatments at any of the three sites and for either of the varieties. First rotation biomass production of 9882-34 ranged from 9.0 to 11.6 Mg ha⁻¹ yr⁻¹ at DEL, 3.4–8.8 Mg ha⁻¹ yr⁻¹ at MID and 3.5–7.7 Mg ha⁻¹ yr⁻¹ at FRE. For SX64, biomass production ranged from 13.2 to 19.0 Mg ha⁻¹ yr⁻¹ at DEL, 9.0–15.0 Mg ha⁻¹ yr⁻¹ at Mid and 5.5–9.3 Mg ha⁻¹ yr⁻¹ at FRE. SX64 deployed small numbers of large stems and produced more biomass than 9882-34 which deployed large numbers of small stems. Application of BC significantly increased soil N and P levels at MID in both 2008 and 2009 (p < 0.05). At DEL, BC and DM treatments increased soil N, Ca, Mg and OM levels in both 2008 and 2009 (p < 0.05). The fertilization treatments had no significant effect on any soil nutrients at FRE. This study indicates that willow biomass can be produced without fertilizer additions in the first rotation across this range of sites due to the nutrient status of these sites and high internal nutrient cycling in these systems.     

Cool-season grasses produce more total biomass across the growing season than do warm-season grasses when managed with an applied irrigation gradient

Warm-season grasses have shown great potential for biomass production. However, their productivity under irrigated conditions has not been thoroughly documented. This study evaluated the biomass production potential and production stability of a number of warm- and cool-season grasses across an irrigation gradient. Under the multiple-harvest management strategy, the cool-season grasses were most productive across the entire growing season. Nevertheless, when considering only the summer harvests, the switchgrass and big bluestem entries were the most productive, although the lowland cultivar Alamo did not perform well under the conditions. Overall, cool-season grasses were clearly the most productive for total biomass production across the growing season. However, based on the high biomass production of switchgrass, this species may have potential as a high-producing option for animal feed during the summer months when the cool-season grasses are unproductive.     

Evaluation of biogas production from different biomass wastes with/without hydrothermal pretreatment

Municipal biomass waste is regarded as new available energy source, although it could cause serious environmental pollution. Generally, biogas recovery by anaerobic digestion was seen as an ideal way to treat biomass waste. Different types of biomass waste have different biogas production potential. In this paper, cow manure, pig manure, municipal sewage sludge, fruit/vegetable waste, and food waste were chosen as typical municipal biomass waste. In addition, hydrothermal pretreatment was used to accelerate digestion and increase biogas production. Biochemical methane potential (BMP) test was used to evaluate biogas production for raw biomass and hydrothermal treated waste. Raw materials of fruit/vegetable and food waste show higher methane production than that of cow manure, pig manure, and municipal sewage sludge. After hydrothermal pretreatment at typical condition (170 °C at 1 h), the biogas production of pig manure, cow manure, fruit/vegetable waste, and municipal sewage sludge increased by 7.8, 13.3, 18.5, and 67.8% respectively. While, for treated food waste, the biogas decrease by 3.4%. The methane yield of pig manure, fruit/vegetable waste, and municipal sewage sludge increased by 14.6, 16.1, and 65.8%, respectively. While, for treated cow manure and food waste, the methane decrease by 6.9% and 7.5%.     

Effect of fertilization on the biomass production of coppiced mixed birch and willow stands on a cut-away peatland

This investigation deals with the biomass production of coppiced mixed birch and willow stands growing on a peat cut-away area at Aitoneva, Kihniö (62°12′N, 23°18′E), Finland. The 16-year-old stands were harvested and left to coppice for 14 years, fertilization experiment (control, PK and wood ash fertilization) with three replications was established after the clear cutting. The mother stands before clear cutting (11,000 stems per hectare on average) were dominated by silver birch (69% of the stem number). After clear cutting the number of stems rose 7-fold to 75 500 stems ha⁻¹. Now the stands were dominated by Betula pubescens with 46% out of the total stem number, the share of B. pendula being only 25% and with Salix spp 29%. At the age of 14 years self-thinning had decreased the stem number to 12,800 stems ha⁻¹. The leafless biomass production of the coppiced stands on the control plots was lower than that of the seed originated mother stands had been during the previous rotation. However, with fertilization the 14-year-old coppiced stands reached the same total production as the 16-year-old mother stands had reached. The foliar phosphorus concentrations showed a severe phosphorus deficiency on the controls. Fertilization increased biomass of the stands considerably. After 14 growing seasons the above-ground leafless dry-mass of the fertilized stands was 61.8 (PK-fertilization) and 61.4 t ha⁻¹ (Ash) and that of the control stands 37.6 t ha⁻¹. A single PK fertilizer application had increased the standing biomass by 24 t ha⁻¹ (64%). Even though fertilization increased biomass production it did not increase nutrient concentrations of wood and bark, but rather decreased them. Fertilization decreased the nitrogen concentrations of leafless above-ground biomass.     

Nitrogen mineralization of sewage sludge and composted poultry manure applied to willow in a greenhouse experiment

Nitrogen requirements for production of intensively cultured willow for use as a bioenergy crop coupled with the need for safe disposal of nutrient rich organic wastes provide an opportunity to reduce costs associated with bioenergy plantations. In order to minimize N leaching from sites treated with organic wastes, knowledge of the rate of N mineralization is needed. The objective of this study was to assess N mineralization rates of four organic residuals in a controlled greenhouse environment: composted poultry manure, composted sewage sludge, and anaerobically digested sewage sludge from two different municipalities. Thirty-six weeks after application, disappearance of the mass initially applied ranged from 20% to 50%. Gross nitrogen mineralization rate (N mass released expressed as a percentage of initially applied N) ranged from 12% to 57%. Non-composted treatments released greater amounts of nitrogen than composted treatments. Within composted treatments, net N release was estimated as 325 kgNha⁻¹ for poultry manure and 86 kgNha⁻¹ for sewage sludge. Syracuse and New York City sewage sludges, with 57% and 30% gross N release rates respectively, provided approximately 360 and 240 kg plant available Nha⁻¹, respectively. These estimates of N release suggest that the application rates could be halved and that sufficient N would be provided to meet crop needs and reduce leaching losses.     

Tracing N, K, Mg and Ca released from decomposing biomass to new tree growth. Part I: A model system simulating harvest residue decomposition on conventionally harvested clearfell sites

It is necessary to assess the effects of removing nutrient-rich harvest residues (brash) from clearfell sites because there is a growing market for this brash as bioenergy. The aim of this study was to use stable isotope techniques in a model system to trace nutrients released by decomposing brash. Labelled biomass was obtained by growing Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings with a generous or poor nutrient supply containing elevated ¹⁵N, ⁴¹K, ²⁶Mg, and ⁴⁴Ca. This biomass was used in two subsequent studies. In this study (Part I of II), the above-ground biomass was harvested and placed on soil in a pot containing a newly planted seedling. Soils from two forests, Ae and Teindland, of contrasting nutritional status were used. A full destructive harvest was undertaken after one growing season. Enriched ¹⁵N, ⁴¹K, ²⁶Mg, and ⁴⁴Ca were recovered in the new seedlings. The percentage contribution from labelled biomass to new tree growth was small, but discernible. The N contribution from labelled biomass to new trees was greater in Ae soil, but the base cation contribution was greater in Teindland soil. Results are discussed with reference to the initial nutrient concentrations of each soil. The elevated ¹⁵N, ⁴¹K, ²⁶Mg and ⁴⁴Ca in new seedlings indicate that nutrients in brash can make a direct contribution to new tree growth. The success of this model system will provide guidance for the application of similar techniques in field experiments.     

Biohydrogen production from oil palm frond juice and sewage sludge by a metabolically engineered Escherichia coli strain

Biohydrogen is considered a promising and environmentally friendly energy source. Escherichia coli BW25113 hyaB hybC hycA fdoG frdc ldhA aceE has been previously engineered for elevated biohydrogen production from glucose. In this study, we show that this strain can also use biomass from oil palm frond (OPF) juice and sewage sludge as substrates. Substrate improvement was accomplished when hydrogen productivity increased 8-fold after enzymatic treatment of the sludge with a mixture of amylase and cellulase. The OPF juice with sewage sludge provided an optimum carbon/nitrogen ratio since the yield of biohydrogen increased to 1.5 from 1.3 mol H₂/mol glucose compared to our previous study. In this study, we also reveal that our engineered strain improved 200-fold biohydrogen productivity from biomass sources compared to the unmodified host. In conclusion, we determined that our engineered strain can use biomass as an alternative substrate for enhanced biohydrogen production.     

Biochemical assays of potential methane to test biogas production from dark fermentation of sewage sludge and agricultural residues

This study aims to study the methane generation potential (BMP tests) of different samples from the dark acid fermentation of sewage sludge:wine vinasse, and sewage sludge:wine vinasse:poultry manure. Specifically, mixtures of sewage sludge (S) and wine vinasse (V) were used in a 50:50 ratio and mixtures of sewage sludge and wine vinasse with 10 g/L of poultry manure (PM) (50:50 + 10 g/L) (S:V + PM). The goal was to determine the effect of the high ammonia concentrations in poultry manure when was used as co-substrate in the anaerobic methanogenic degradation of sewage sludge and vinasse. Results obtained show that the addition of 10 g/L of poultry manure to the SV mixture improves the production of methane generation, reaching values of 166 mL of accumulated methane. The SVPM mixture shows the highest purification percentages, with 63.90% TCOD removal, 79.51% SCOD removal and a yield of 52.05 mLCH₄/gSV_added. The SVPM test showed a higher concentration of microorganisms during the BMP test, although the population of microorganisms for the SV test was doubled and presented greater activity with values of 2.27 versus 1.73E-11 LCH₄/Cells.     

Wood ash effects on plant and soil in a willow bioenergy plantation

Intensive management for biomass production results in high rates of nutrient removal by harvesting. We tested whether wood ash generated when burning wood for energy could be used to ameliorate negative soil effects of short-rotation harvesting practices. We measured the temporal and spatial dynamics of soil nutrient properties after wood ash applications in a willow plantation in central New York State and determined the influence of wood ash application on willow growth. Wood ash was applied annually for 3 years at the rates of 10 and 20 Mg ha⁻¹ to coppiced willow, Salix purpurea, clone SP3. Wood ash application significantly increased soil pH in the 0–10 cm soil layer from 6.1 in the control to 6.9 and 7.1 in the 10 and 20 Mg ha⁻¹ treated plots. Wood ash application significantly increased soil extractable phosphorus, potassium, calcium, and magnesium concentrations. Potassium was the element most affected by wood ash treatment at all soil depths. Wood ash had no significant effect on nutrient concentrations of foliar, litter, and stem tissue. Wood ash did not affect either individual plant growth or plot biomass production, which declined over the course of the study; it did increase the size of stems, but this effect was balanced by a decrease in the number of stems. Applying nitrogen as well as wood ash might be required to maintain the productivity of this SRIC system.     

Switchgrass simulation by the ALMANAC model at diverse sites in the southern US

Simulation models for plant species important for biofuel such as switchgrass (Panicum virgatum L.) can be used to make management decisions related to biomass productivity and related to environmental impacts such as soil erosion and changes in surface and groundwater quality. The present study was designed to evaluate the accuracy of simulation of switchgrass biomass production by the ALMANAC (Agricultural Land Management Alternatives with Numerical Assessment Criteria) model at sites in Texas, Arkansas, and Louisiana. We used multi-year field data for Alamo switchgrass yields at each of five sites to evaluate ALMANAC. The model realistically simulated mean switchgrass yields at each of the locations and the total variability of all the data pooled, but did not perform as well in accounting for the year-to-year variability within some locations. Sensitivity analysis showed that changes in runoff curve number (CN) and changes in maximum stomatal conductance (GSI) had variable impacts on simulated values among the sites. A 15% change in CN changed mean annual biomass yield from 0% to 16% depending on location. Changing GSI from 4 to 8 mm s⁻¹ changed mean annual biomass from 1% to 31% depending on location. ALMANAC shows promise as a tool to realistically simulate mean biomass yields and variability around the mean for multi-year runs of switchgrass at these diverse sites. Further research, with more extensive measurements of soil parameters including soil nutrients is needed to determine why the model reasonably simulated individual years’ yields at Stephenville, TX and Dallas, TX, but had difficulty at other sites.     

Neochloris oleoabundans grown on anaerobically digested dairy manure for concomitant nutrient removal and biodiesel feedstock production

Microalgae have been investigated as a promising biodiesel feedstock; however, large-scale production is not currently cost-competitive with petroleum diesel, and its environmental impacts have received little attention. Using wastewater to supply nutrients for algal growth obviates synthetic fertilizer use, provides on-site nutrient removal, and reduces greenhouse gas emissions. In this work, anaerobically digested dairy manure was used to grow the oleaginous green alga Neochloris oleoabundans. In batch culture experiments with both synthetic media and anaerobic digester effluent, N. oleoabundans assimilated 90-95% of the initial nitrate and ammonium after 6 d and yielded 10-30% fatty acid methyl esters on a dry weight basis. Cellular lipid content and the N concentration in the growth media were inversely correlated. In addition, the proportion of polyunsaturated fatty acids (i.e. C16:3, C18:2, and C18:3) decreased with N concentration over time while the proportion of C18:1 fatty acid increased. Although N deficiency is likely the primary driver behind lipid accumulation, the influence of culture pH confounded results and requires further study. Other living microorganisms in the digester effluent were not observed to affect algal growth and lipid productivity, though the breakdown of organic nitrogen may have hindered lipid accumulation traditionally achieved through the manipulation of synthetic media. This work highlights the potential for waste-grown mono-algal cultures to produce high quality biodiesel while accomplishing simultaneous wastewater treatment.