Biomass For Bioenergy Research Articles

Biomass production and carbon sequestration of a short-rotation forest with different poplar clones in northwest China

Short Rotation Forestry (SRF) is of interest as producers of biomass for bio-energy, but also as carbon (C) sinks to mitigate CO2 emission. To investigate biomass production and C sequestration of SRF, ecosystem C stock (including C stored in tree biomass, litter and soil), NPP (net primary productivity), heterotrophic respiration (Rh) and NEP (net ecosystem productivity) of three poplar clone plantations were estimated by repeated field sampling in northwest China. Ecosystem C stock (105.62MgCha−1) was significantly lower in PB (P. balsamifera) stand than in PD (P. deltoids) and PE (P.×euramericana) stands (P<0.01). Biomass C stock was greatly affected by clone type (P<0.01), while significant difference in soil C stock was not detected. Averaged NPP was 8.80MgCha−1yr−1 across all clone stands, but the most productive clone of PD yielded up to 10.72MgCha−1yr−1. NEP was found to be significantly different among the clone stands, increasing from 0.21MgCha−1yr−1 in PB to 6.77MgCha−1yr−1 in PD stand. With soil C outputs (Rh) being smaller than C sequestrations, the plantations all acted as C sinks, averagely absorbing 3.45MgCha−1 during a year. Our results suggest that clone type is a main factor influencing C sequestration capacity of a plantation, along with determining the amount of biomass yield. The success of poplar plantations as a bio-energy resource largely depends on the selection of hybrid varieties.

Improving water quality in the Chesapeake Bay using payments for ecosystem services for perennial biomass for bioenergy and biofuel production

Replacing row crops with perennial bioenergy crops may reduce nitrogen (N) loading to surface waters. We estimated the benefits, costs, and potential for replacing maize with switchgrass to meet required N loading reduction targets for the Chesapeake Bay (CB) of 26.9 Gg y−1. After subtracting the potential reduction in N loading due to improved N fertilizer practices for maize, a further 22.8 Gg y−1 reduction is required. Replacing maize with fertilized switchgrass could reduce N loading to the CB by 18 kg ha−1 y−1, meeting 31% of the N reduction target. The break-even price of fertilized switchgrass to provide the same profit as maize in the CB is 111 $ Mg−1 (oven-dry basis throughout). Growers replacing maize with switchgrass could receive an ecosystem service payment of 148 $ ha−1 based on the price paid in Maryland for planting a rye cover crop. For our estimated average switchgrass yield of 9.9 Mg ha−1, and the greater N loading reduction of switchgrass compared to a cover crop, this equates to 24 $ Mg−1. The annual cost of this ecosystem service payment to induce switchgrass planting is 13.29 $ kg−1 of N. Using the POLYSYS model to account for competition among food, feed, and biomass markets, we found that with the ecosystem service payment for switchgrass of 25 $ Mg−1 added to a farm-gate price of 111 $ Mg−1, 11% of the N loading reduction target could be met while also producing 1.3 Tg of switchgrass, potentially yielding 420 dam3 y−1 of ethanol.

A critical analysis of species selection and high vs. low-input silviculture on establishment success and early productivity of model short-rotation wood-energy cropping systems

Most research on bioenergy short rotation woody crops (SRWC) has been dedicated to the genera Populus and Salix. These species generally require relatively high-input culture, including intensive weed competition control, which increases costs and environmental externalities. Widespread native early successional species, characterized by high productivity and good coppicing ability, may be better adapted to local environmental stresses and therefore could offer alternative low-input bioenergy production systems. To test this concept, we established a three-year experiment comparing a widely-used hybrid poplar (Populus nigra × P. maximowiczii, clone ‘NM6’) to two native species, American sycamore (Platanus occidentalis L.) and tuliptree (Liriodendron tulipifera L.) grown under contrasting weed and pest control at a coastal plain site in eastern North Carolina, USA. Mean cumulative aboveground wood production was significantly greater in sycamore, with yields of 46.6 Mg ha−1 under high-inputs and 32.7 Mg ha−1 under low-input culture, which rivaled the high-input NM6 yield of 32.9 Mg ha−1. NM6 under low-input management provided noncompetitive yield of 6.2 Mg ha−1. Sycamore also showed superiority in survival, biomass increment, weed resistance, treatment convergence, and within-stand uniformity. All are important characteristics for a bioenergy feedstock crop species, leading to reliable establishment and efficient biomass production. Poor performance in all traits was found for tuliptree, with a maximum yield of 1.2 Mg ha−1, suggesting this native species is a poor choice for SRWC. We conclude that careful species selection beyond the conventionally used genera may enhance reliability and decrease negative environmental impacts of the bioenergy biomass production sector.

Biomass from young hardwood stands on marginal lands: Allometric equations and sampling methods

We developed allometric equations for small-diameter woody species growing on mixed forest marginal lands, which are potential sources of biomass for bioenergy. Eleven species of trees and shrubs were sampled from a site located in eastern Canada. Equations derived in this study generally performed better than equations from the literature. Also, fixed-area plots (FAP) and line-intersect sampling (LIS) methods using both random or systematic selection of sampling units were compared to determine which method required the lowest number of measurements to estimate stand biomass for the same precision.The fixed-area plots method was successfully used to estimate relatively accurately oven-dry biomass per hectare. Results indicated that potentially harvestable woody biomass (oven dry basis) varied between 33-41 and 12–13 t ha−1 for the most and least productive marginal sites respectively. On the most productive site, LIS estimates (between 20 and 42 t ha−1) were usually lower than those obtained using different FAP sampling methods (i.e. systematic or random, small (50 m2) or large (100 m2) plots), but similar on the more open sites (between 10 and 14 t ha−1). Small FAP resulted in a plot without measurements in one case. Moreover, estimates based on small FAP were generally higher, even if not significantly different from larger plot estimates. We therefore suggest using FAP with 100 m2 plots to estimate small-diameter woody biomass on marginal lands with dense vegetation, while LIS, even if promising for open stands, needs further evaluation before recommendation.

Simulating Establishment Periods of Switchgrass and Miscanthus in the Soil and Water Assessment Tool (SWAT)

Abstract. The establishment periods of switchgrass and can be a time window when evapotranspiration, surface runoff generation, and sediment and nutrients losses are quite different from when the grasses become fully established, and this period may result in environmental concerns for large-scale biomass production. The current SWAT model does not simulate the establishment periods of perennial grasses. In this study, we modified the model to simulate these periods by updating the maximum annual leaf area index (LAI) instead of using a static value in the unmodified model. The improved SWAT model provided more realistic simulations of LAI values and yields comparable to observed yields from field plots during the establishment periods of the two perennial grasses. The modification made in the present study enabled the SWAT model to be more suitable for evaluating perennial biomass grass-related scenarios. Keywords: Biomass bioenergy, Establishment period, Miscanthus, SWAT, Switchgrass.

The Land-Use Consequences of Woody Biomass with More Stringent Climate Mitigation Scenarios

Integrated assessment models increasingly rely on biomass for energy with ever more stringent mitigation policies. The stringency of mitigation will therefore have large effects on land use. As discussed in the literature, crop bio-energy will lead to substantial pressure to increase deforestation. This paper consequently explores using woody biomass for bioenergy. The paper combines the IAM WITCH with a global dynamic forestry model GTM to determine the optimal size of the woody biomass market, the effects on the timber market, and the resulting forestland under two alternative mitigation strategies. This paper predicts that moving from a moderate to a stringent mitigation policy would increase the demand for woody biomass from 3.7 to 5.2 billion m3/yr, increasing forestland by 1049 to 1890 million ha, and shrinking farmland by 748 to 1550 million ha. The stringency of mitigation will therefore have large effects on land use.

Annual bioenergy crops for biofuels production: Farmers' contractual preferences for producing sweet sorghum

Dedicated annual sorghum crops, such as sweet sorghum or energy sorghum, may provide an option for farmers to supply cellulosic feedstocks for biofuel production and help the industry meet government mandates. Kansas farmers are poised to be major producers of sweet sorghum for biofuels due to favorable agro-ecological conditions. The purpose of this paper is to assess Kansas farmers' willingness to grow sweet sorghum under contract as a feedstock for biofuel production. The paper examines farmers' willingness-to-pay for contract attributes and the impact of socio-economic factors on their willingness-to-pay for these attributes. A stated choice survey was administered to Kansas farmers to assess their willingness to grow sweet sorghum for biofuels under various contracting scenarios. Results show that farmers may be willing to grow biomass for bioenergy under contract, but may have varying preferences for the importance of contract attributes such as net returns, contract length, insurance availability, government incentives, and potential for biorefinery harvest options based on socio-economic characteristics of growers.

Land-use futures in the shared socio-economic pathways

Abstract In the future, the land system will be facing new intersecting challenges. While food demand, especially for resource-intensive livestock based commodities, is expected to increase, the terrestrial system has large potentials for climate change mitigation through improved agricultural management, providing biomass for bioenergy, and conserving or even enhancing carbon stocks of ecosystems. However, uncertainties in future socio-economic land use drivers may result in very different land-use dynamics and consequences for land-based ecosystem services. This is the first study with a systematic interpretation of the Shared Socio-Economic Pathways (SSPs) in terms of possible land-use changes and their consequences for the agricultural system, food provision and prices as well as greenhouse gas emissions. Therefore, five alternative Integrated Assessment Models with distinctive land-use modules have been used for the translation of the SSP narratives into quantitative projections. The model results reflect the general storylines of the SSPs and indicate a broad range of potential land-use futures with global agricultural land of 4900 mio ha in 2005 decreasing by 743 mio ha until 2100 at the lower (SSP1) and increasing by 1080 mio ha (SSP3) at the upper end. Greenhouse gas emissions from land use and land use change, as a direct outcome of these diverse land-use dynamics, and agricultural production systems differ strongly across SSPs (e.g. cumulative land use change emissions between 2005 and 2100 range from −54 to 402 Gt CO2). The inclusion of land-based mitigation efforts, particularly those in the most ambitious mitigation scenarios, further broadens the range of potential land futures and can strongly affect greenhouse gas dynamics and food prices. In general, it can be concluded that low demand for agricultural commodities, rapid growth in agricultural productivity and globalized trade, all most pronounced in a SSP1 world, have the potential to enhance the extent of natural ecosystems, lead to lowest greenhouse gas emissions from the land system and decrease food prices over time. The SSP-based land use pathways presented in this paper aim at supporting future climate research and provide the basis for further regional integrated assessments, biodiversity research and climate impact analysis.

European forests show no carbon debt, only a long parity effect

In the past the use of woody biomass for bioenergy was considered carbon neutral. However, this changed when analyses were made of cases of land use change or old growth forest logging for bioenergy purposes. These analyses showed a significant carbon debt that could take hundreds of years to be compensated by the substitution factor of the bioenergy.Currently, carbon debt analyses are often carried out: 1) at one hectare scale, or 2) against the hypothetical case of allowing the managed forest to grow to an old-growth state, or 3) in a comparison against short term policy goals. All three are not realistic for European forests. Here we analysed carbon debt and parity of realistically increased harvesting over large forest areas in Europe. We found that under such realistic cases, a carbon debt does not occur. i.e. the large scale average stocks in the forest are not reduced. What does occur is a parity compared to the baseline harvesting levels. The parity effect was eventually also compensated for. However it took long, especially if final fellings were increased for bioenergy; which is a rather hypothetical case. In case of increased thinnings, the parity equality was often reached within 80years compared to burning coal. Removal of harvesting residues was often compensated within 1 decade. However, parity is a theoretical comparison against a higher baseline C stock in the forest. It is not certain that this higher stocking under the baseline will be sustained, because there is an increasing chance of natural disturbances. Thus the parity may be much shorter than analysed here.

Electrochemical Oxidation of Lignin for Production of Value Added Chemicals

Electrochemical oxidation of lignin for production of value added chemicals Raziyeh Ghahremani and John A. Staser (Center for Electrochemical Engineering Research, Department of Chemical and Biomolecular Engineering, Ohio University) The polyphenolic structure of lignin makes it the ideal raw material to produce commercial aromatic compounds[1]. However, due to the difficulty of the conversion process of lignin, it is usually burned to produce heat and energy[2]. Electrochemical oxidation is an environmentally friendly, inexpensive, and efficient depolymerization process which can take place at relatively low pressure and temperature, and the reaction can be controlled by potential or current[1]. However, high cost of materials for preparing electrodes, also deactivation of the electrode during the reaction due to impurities makes electrochemical oxidation processes more elaborate and expensive, prohibiting its broad application[3]. Therefore, it is critical to develop a low cost and efficient electrode for the electrochemical oxidation of lignin. In this work, the inexpensive Ni-Co electrocatalysts were developed for use in the electrochemical oxidation of lignin to produce other value added chemicals. We have developed nanoparticle electrocatalysts that are suitable for a continuous flow electrochemical reactor to be integrated into existing biorefineries. Gas chromatography and mass spectroscopy (GC-MS) was applied to analyze the products and the results showed that valuable chemicals like vanillin, apocynin and other aromatic compounds are produced by the electrochemical oxidation of lignin, the concentration of chemicals also were increased during the time of oxidation. We will also present techno-economic analyses that can be used as a benchmark for integrating the electrochemical reactor into the biorefinery. [1] O. Movil, M. Garlock, and J. A. Staser, “Non-precious metal nanoparticle electrocatalysts for electrochemical modification of lignin for low-energy and cost-effective production of hydrogen,” Int. J. Hydrog. Energy, vol. 40, no. 13, pp. 4519 – 4530, 2015. [2] D. Klein-Marcuschamer, P. Oleskowicz-Popiel, B. A. Simmons, and H. W. Blanch, “Technoeconomic analysis of biofuels: A wiki-based platform for lignocellulosic biorefineries,” Biomass Bioenergy, vol. 34, no. 12, pp. 1914 – 1921, 2010. [3] Y. Zhang, Y. Peng, X. Yin, Z. Liu, and G. Li, “Degradation of lignin to BHT by electrochemical catalysis on Pb/PbO2 anode in alkaline solution,” J. Chem. Technol. Biotechnol., vol. 89, no. 12, pp. 1954–1960, 2014.

Bioenergy production and forest landscape change in the southeastern United States

AbstractProduction of woody biomass for bioenergy, whether wood pellets or liquid biofuels, has the potential to cause substantial landscape change and concomitant effects on forest ecosystems, but the landscape effects of alternative production scenarios have not been fully assessed. We simulated landscape change from 2010 to 2050 under five scenarios of woody biomass production for wood pellets and liquid biofuels in North Carolina, in the southeastern United States, a region that is a substantial producer of wood biomass for bioenergy and contains high biodiversity. Modeled scenarios varied biomass feedstocks, incorporating harvest of ‘conventional’ forests, which include naturally regenerating as well as planted forests that exist on the landscape even without bioenergy production, as well as purpose‐grown woody crops grown on marginal lands. Results reveal trade‐offs among scenarios in terms of overall forest area and the characteristics of the remaining forest in 2050. Meeting demand for biomass from conventional forests resulted in more total forest land compared with a baseline, business‐as‐usual scenario. However, the remaining forest was composed of more intensively managed forest and less of the bottomland hardwood and longleaf pine habitats that support biodiversity. Converting marginal forest to purpose‐grown crops reduced forest area, but the remaining forest contained more of the critical habitats for biodiversity. Conversion of marginal agricultural lands to purpose‐grown crops resulted in smaller differences from the baseline scenario in terms of forest area and the characteristics of remaining forest habitats. Each scenario affected the dominant type of land‐use change in some regions, especially in the coastal plain that harbors high levels of biodiversity. Our results demonstrate the complex landscape effects of alternative bioenergy scenarios, highlight that the regions most likely to be affected by bioenergy production are also critical for biodiversity, and point to the challenges associated with evaluating bioenergy sustainability.

Perennial species mixtures for multifunctional production of biomass on marginal land

AbstractMultifunctional agriculture provides noncommodity functions and services along with food, feed and bioenergy feedstocks, for example by preserving or promoting biodiversity, improving soil fertility, mitigating climate change and environmental degradation, and contributing to the socio‐economic viability of rural areas. Producing biomass for bioenergy from low‐input perennial species mixtures on marginal land has the potential to support biodiversity and soil carbon sequestration in synergy with greenhouse gas mitigation. We compared biomass production in species‐rich mixtures of perennial grasses, legumes and forbs with pure‐stand grasses and relatively species‐poor mixtures under different nitrogen fertilization regimes. Field experiments were performed on different types of marginal land, that is agricultural field margins and land with poor soil fertility, at four sites in southernmost and western Sweden. Biomass production was measured for three years in perennial grasses grown as pure stands, in legume‐grass mixtures, and legume‐grass‐forb mixtures across a species richness gradient. In unfertilized species‐rich mixtures, average biomass yields per experimental site and year were in the range from 3 to 9 metric ton DM ha−1 yr−1. While the most productive pure‐stand grasses fertilized with 60–120 kg N ha−1 yr−1 often produced higher biomass yields than unfertilized mixtures, these differences were generally smaller than the variations between years and sites. Calculations of climate impact using the harvested biomass for conversion to biogas as vehicle fuel showed that the average greenhouse gas emissions per energy unit were about 50% lower in unfertilized systems than in treatments fertilized with 100–120 kg N ha−1 yr−1. Our findings thereby show that unfertilized species‐rich perennial plant mixtures on marginal land provide resource‐efficient biomass production and contribute to the mitigation of climate change. Perennial species mixtures managed with low inputs thus promote synergies between productivity and biodiversity in the perspective of climate‐smart and multifunctional biomass production.

Wood Bioenergy and Soil Productivity Research

Timber harvesting can cause both short- and long-term changes in forest ecosystem functions, and scientists from USDA Forest Service (USDA FS) have been studying these processes for many years. Biomass and bioenergy markets alter the amount, type, and frequency at which material is harvested, which in turn has similar yet specific impacts on sustainable productivity. The nature of some biomass energy operations provides opportunities to ameliorate or amend forest soils to sustain or improve their productive capacity, and USDA FS scientists are leading the research into these applications. Research efforts to sustain productive soils need to be verified at regional, national, and international scope, and USDA FS scientists work to advance methods for soil quality monitoring and to inform international criteria and indicators. Current and future USDA FS research ranges from detailed soil process studies to regionally important applied research and to broad scale indicator monitoring and trend analysis, all of which will enable the USA to lead in the sustainable production of woody biomass for bioenergy.

Variation in leaf‐level photosynthesis among switchgrass genotypes exposed to low temperatures does not scale with final biomass yield

AbstractThe effect of a 10‐day low‐temperature treatment and subsequent recovery of 13 genotypes of switchgrass, including upland and lowland types, resulted in significant variations in a number of leaf‐level photosynthetic parameters. Whilst the most resistant genotype (Blackwell) is an upland type, there was no clear separation of upland and lowland genotypes in terms of the resistance of leaf photosynthesis (Asat, ϕCO2max, Vp and Vpmax), respiration (Rd) or fluorescence (Fv/Fm) parameters to low temperatures, with lowland types also achieving higher biomass yields than upland types. Examination of the reason for differences in the impact of low temperatures on leaf photosynthesis indicated that this could be due to both PEP carboxylase activity and/or PEP regeneration, but with some support for PEP regeneration being the more important. However, variations in leaf photosynthesis were not related to the final biomass yield in either control or low‐temperature‐exposed plants, and the best correlation was found with leaf area. Low temperatures were found to have a post‐treatment impact on leaf area development through a reduction in the formation of new leaves. Overall, these results suggest that more attention should be directed at variations in the effect of low temperature on leaf initiation and emergence to exploit the wider use of switchgrass as a biomass–bioenergy crop.

A spatial assessment of potential biomass for bioenergy in Australia in 2010, and possible expansion by 2030 and 2050

AbstractThis paper provides spatial estimates of potentially available biomass for bioenergy in Australia in 2010, 2030 and 2050 (under clearly stated assumptions) for the following biomass sources: crop stubble, native grasses, pulpwood and residues (created either during forest harvesting or wood processing) from plantations and native forests, bagasse, organic municipal solid waste and new short‐rotation tree crops. For each biomass type, we estimated annual potential availability at the finest scale possible with readily accessible data, and then aggregated to make estimates for each of 60 Statistical Divisions (administrative areas) across Australia. The potentially available lignocellulosic biomass is estimated at approximately 80 Mt per year, with the major contributors of crop stubble (27.7 Mt per year), grasses (19.7 Mt per year) and forest plantations (10.9 Mt per year). Over the next 20–40 years, total potentially available biomass could increase to 100–115 Mt per year, with new plantings of short‐rotation trees being the major source of the increase (14.7 Mt per year by 2030 and 29.3 Mt per year by 2050). We exclude oilseeds, algae and ‘regrowth’, that is woody vegetation naturally regenerating on previously cleared land, which may be important in several regions of Australia (Australian Forestry 77, 2014, 1; Global Change Biology Bioenergy 7, 2015, 497). We briefly discuss some of the challenges to providing a reliable and sustainable supply of the large amounts of biomass required to build a bioenergy industry of significant scale. More detailed regional analyses, including of the costs of delivered biomass, logistics and economics of harvest, transport and storage, competing markets for biomass and a full assessment of the sustainability of production are needed to underpin investment in specific conversion facilities (e.g. Opportunities for forest bioenergy: An assessment of the environmental and economic opportunities and constraints associated with bioenergy production from biomass resources in two prospective regions of Australia, 2011a).

Review: Assessing the climate mitigation potential of biomass

For many millennia, humans have used biomass for three broad purposes: food for humans and fodder for farm animals; energy; and materials. Food has always been exclusively produced from biomass, and in the year 1800, biomass still accounted for about 95% of all energy. Biomass has also been a major source of materials for construction, implements, clothing, bedding and other uses, but some researchers think that total human uses of biomass will soon reach limits of sustainability. It is thus important to select those biomass uses that will maximise global climate change benefits. With a ‘food first’ policy, it is increasingly recognised that projections of food needs are important for estimating future global bioenergy potential, and that non-food uses of biomass can be increased by both food crop yield improvements and dietary changes. However, few researchers have explicitly included future biomaterials production as a factor in bioenergy potential. Although biomaterials’ share of the materials market has roughly halved over the past quarter-century, we show that per tonne of biomass, biomaterials will usually allow greater greenhouse gas reductions than directly using biomass for bioenergy. particularly since in many cases, biomaterials can be later burnt for energy after their useful life.

A Linear Programming Optimization Model of Woody Biomass Logistics Integrating Infield Drying as a Cost-Saving Preprocess in Michigan

Abstract Because of the greater demand in using woody biomass for bioenergy and bio-based products, feedstock supply chain optimization becomes more important to decrease supply chain logistics costs. As a primary component in the biomass feedstock supply chain, the storage of harvested woody biomass can directly affect transportation cost, biomass quality, and combustion efficiency. An improved operations system structured with linear programming was developed for minimizing the total cost of woody biomass preprocessing, storage, and transportation. The improved operations system was applied in a simulated case study for a power plant in Michigan. In addition, a simulated second feedstock end user was added to the operations system to further test the model. The results showed that the improved operations system could lower supply chain logistics costs, improve feedstock quality, and simultaneously meet the feedstock end user's demand. The sensitivity analysis indicated that the additional profit from selling higher-quality feedstock could offset the increased transportation cost for up to 171 miles. On average, every 1 percent decrease in biomass moisture content can result in a decrease of $760.68 in total cost and a reduction of 52.1 green tons of delivered biomass to satisfy the end user's demands. The operation details suggested by the improved operations system can be used as a guideline of real operations to achieve the lowest possible operations cost. The additional profit return from selling higher-quality feedstock needs to be quantified for various conversion and upgrading options besides direct combustion in the future.

Oil-rich nonseed tissues for enhancing plant oil production.

Abstract Plants are being engineered for enhanced ethanol production; however, challenges remain in meeting the demand for bioenergy that is expected to double by 2030. Therefore, targeting carbon accumulation in the form of energy-dense oils in nonseed biomass is considered a superior alternative for bioenergy production. Although oils in the form of triacylglycerols (TAGs) are typically stored in seed tissues, various nonseed tissues such as mesocarp, tubers, stems and leaves also serve as storage tissues for TAG accumulation in plants. Moreover, the biomass of these tissues is generally far greater than seed biomass. In order to increase oil content in nonseed biomass for bioenergy and nutritional purposes, it is important to understand how such plants naturally accumulate TAG in nonseed tissues. Several molecular approaches, including transcriptomics, have been undertaken to elucidate the metabolic and regulatory mechanisms of carbon partitioning in oil-rich nonseed tissues. Such studies are expected to generate important transgenic tools that can be used to alter fatty acid metabolism and engineer plants to produce oil-rich biomass successfully. This review focuses on the potential of different oil-rich nonseed tissues and the strategies developed for enhancing oil biomass.

A Review on Biogas Interception Processes in Municipal Landfill

Biogas in landfill is being captured by natural and engineered processes. The natural processes are represented by biological activities such as bacterial methane oxidation and plant uptake for carbon dioxide at topsoil layer. Landfill gas is transported through soil layers in landfill top or in nearby areas before being released to the atmosphere. Whilst transported in the soil layers the biogas is mixed with atmospheric air and the methane may hence be oxidized by the methanotrophic bacteria in the soil using oxygen from atmosphere. Methane oxidation is affected by different environmental factors such as; temperature, water content, nutrients, substrate and oxygen concentrations. One of the ways to decrease greenhouse emissions in the future is to plant fast growing woody crops thereby sequestering carbon and displacing fossil fuels by harvesting woody biomass for bio-energy, or by storing carbon in long-lived woody products. Plant uptake for carbon dioxide is affected by some parameters such as; CO2 concentration, nitrogen concentration, water content and temperature. The engineered processes are represented by various physical biogas extractions; gas is collected using network of collection pipes and wells. The gas collection efficiency in landfills is between 40-90%. Landfill gas can be collected by either a passive or an active collection system. Passive gas collection systems use existing variations in landfill pressure and gas concentrations to vent landfill gas into the atmosphere or a control system. Active gas collection is considered a good means of landfill gas collection. An active collection system composed of extraction wells connected to header pipe to a pump that delivers gas for energy recovery.

Herbicide management of invasive cattail (Typha × glauca) increases porewater nutrient concentrations

Invasive wetland plants are the primary targets of wetland management to promote native communities and wildlife habitat, but little is known about how commonly implemented restoration techniques influence nutrient cycling. We tested how experimental mowing, herbicide application, and biomass harvest (i.e., removal of aboveground biomass) treatments of Typha-invaded mesocosms altered porewater nutrient (NO3 −, NH4 +, PO 4 −3 ) concentration and supply rate, vegetation response, and light penetration to the soil surface. We found that while herbicide application eliminated the target species, it also reduced native plant density and biomass, as well as increased porewater nutrient concentration (PO 4 −3 , NO3 −) and supply rates (N, P, K) up to a year after treatments were implemented. Because herbicide application promotes nutrient enrichment, it may increase the likelihood of reinvasion by problematic wetland invaders, as well as cause eutrophication and deleterious algal blooms in adjacent aquatic systems. Our data suggest that biomass harvest should be considered by managers aiming to reduce Typha abundance without eradicating native diversity, avoid nutrient leaching, as well as possibly utilizing biomass for bioenergy.