Green biomass to biogas – A study on anaerobic digestion of residue grass (original) (raw)
Related papers
Energy recovery of grass biomass
Energy and Sustainability III, 2011
Not only due to the actual climate change, but also in consideration of exhaustible resources, alternative energy supplies for the steadily growing energy demand need to be found. The main emphasis should be placed on the substitution of fossil fuels with agricultural by-products and other organic materials. The utilisation of fresh grass or grass silage of extensively cultivated farm land especially has great potential as an energy feedstock, as in agriculture this bio-resource is currently considered a waste material and is neither economically nor ecologically utilised in an efficient way. Additionally, the lawn-clippings, which are accumulating as communal and private waste could be used for energy production since many local authorities have problems with utilising this gramineous waste. Thus, for anaerobic digestion big amounts of grass biomass and lawn substrates are available from farmers and landscape conservation. In order to evaluate the suitability of this material for biogas plants in the first place a detailed inventory needs to be conducted. This was exemplarily done for the Hamburg District Bergedorf (155 km 2). The result shows that approximately 10,000 Mg/a of grass and lawn clippings could theoretically be made available. By laboratory investigations in batch tests the theoretical biogas potentials of selected grass and lawn substrates were determined. A statement about the suitability of the substrates for anaerobic digestion is made in this paper. The biogas potentials are between 325 and 720 standardized l per kg organic dry matter (l/kg ODM), depending on the sampling location, mowing time, grass species etc. For example, the biogas potentials for clippings from the dikes were in a range comparable with corn silage between 420 to 700 l/kg ODM. Additionally the problem of seasonal accumulation of grass biomass including the influence of storage on the initial material is considered in this paper.
The Potential for Biogas Production from Grass
2011
Grass is generally considered as one of the major agricultural products and covers over 90% of Irish agricultural land. While useful as an animal feedstock it can also be used for energy production. Here batch mesophilic anaerobic digestion of grass silage was studied. The methane concentration in the biogas clearly showed that grass silage has a high affinity to produce a high quality methane steam between 70-80%. Investigation of the effect of inoculum to substrate ratio on methane yield from grass silage using BMP (batch) anaerobic digester under mesophilic conditions, showed that the optimum I/S ratio is approximately 1 with a maximum methane yield of 0.385 m 3 kg - 1 COD.
A Review of Biogas Production Optimization from Grass Silage
Int'l Conf. on Chemical Engineering & Advanced Computational Technologies (ICCEACT’2014) Nov. 24-25, 2014 Pretoria (South Africa)
Anaerobic digestion (AD) of organic materials offers an alternative source of renewable energy, as bio-methane has a potential to replace fossil fuels for energy production for heat and power, vehicular fuel and as well as valuable material recovery. In addition AD can address pollution problems by minimizing and utilizing biodegradable waste. This a well-researched and technologically advanced technique with various successful small to large scale plants in the developed world. For developing countries, not much success has been reported due to operational and maintenance challenges, low biogas production and public perceptions among other several contributing factors. This paper reviews AD process optimization focusing on parameters such as temperature, pH, loading rate, hydraulic retention time and agitation. Several studies have shown optimum biogas production from grass in mesophilic, alkaline or neutral conditions at retention times of about 30 days. This review is the background and basis of our current work on optimizing biogas production from selected South African grass species.
Sustainability, 2016
This paper analyses the comparative advantage of using silage maize or grass as feedstock for anaerobic digestion to biogas from a greenhouse gas (GHG) mitigation point of view, taking into account site-specific yield potentials, management options, and land-use change effects. GHG emissions due to the production of biogas were calculated using a life-cycle assessment approach for three different site conditions with specific yield potentials and adjusted management options. While for the use of silage maize, GHG emissions per energy unit were the same for different yield potentials, and the emissions varied substantially for different grassland systems. Without land-use change effects, silage maize-based biogas had lower GHG emissions per energy unit compared to grass-based biogas. Taking land-use change into account, results in a comparative advantage of biogas production from grass-based feedstock produced on arable land compared to silage maize-based feedstock. However, under current frame conditions, it is quite unrealistic that grass production systems would be established on arable land at larger scale.
Green Grass: Developing Grass for Sustainable Gaseous Biofuel.pdf
Grass is ubiquitous in Ireland and temperature northern Europe. It is a low input perennial crop; farmers are well versed in its production and storage (ensiling). Anaerobic digestion is a well understood technology. However the level of comfort with the technology can mask the difficulties associated with digestion of high solid content feedstocks especially grass silage. It is not simply a matter of using a digester designed for slurry or for Maize to produce biogas from grass silage. Grass is a lignocellulosic feedstock which is fibrous; it can readily cause difficulties with moving parts (wrapping around mixers); it also has a tendency to float. This thesis has an ambition of establishing the ideal digester configuration for production of biogas from grass. Extensive analysis of the literature is undertaken on the optimal production of grass silage and the associated biodigester configurations. As a result of this analysis two different digester systems were designed, fabricated, commissioned and operated for over a year. The first system was a two stage wet continuous system commonly referred to as a Continuously Stirred Tank Reactor (SCTR). The second was a two stage, two phase system employing Sequentially Fed Leach Beds complete with an Upflow Anaerobic Sludge Blanket (SLBR-UASB). These were operated on the same grass silage cut from the same field at the same time. Small biomethane potential (BMP) assays were also evaluated for the same grass silage. The results indicated that the CSTR system produced 451 L CH4 kg-1 VS added at a retention time of 50 days while effecting a 90% destruction in volatile dry solids. The SLBR-UASB produced 341 L CH4 kg-1 VS added effecting a 75% reduction in volatile solids at a retention time of 30 days. The BMP assays generated results in the range 350 to 493 L CH4 kg-1 VS added. This thesis concludes that a disparity exists in the BMP tests used in the industry. It is suggested that the larger BMP (2L with a 1.5 L working volume) gives a good upper limit on methane production. The micro BMP (100 ml) gave a relatively low result. The CSTR when designed specifically for grass silage is shown to be extremely effective in methane production. The SLBR-UASB has significant potential to allow for lower retention times with good levels of methane production. This technology has more potential for research and improvement especially in enzymatic hydrolysis and for use of digestate in added value products.
Biogas from Fresh Spring and Summer Grass: Effect of the Harvesting Period
Energies
Yard trimmings, landscape management and agricultural practices determine the collection of biomass currently destined mainly to the production of a valuable soil amendant by composting. While composting requires energy, especially for the turning/aeration phases and for air treatment (i.e., biofilters in the case of enclosed systems), anaerobic digestion represents an energy positive process that results in production of biogas and digestate, which can be used as fuel and fertilizer, respectively. The focus of the present research was the evaluation of biogas and methane potential of grass collected in two different periods of the year (spring and summer) from riverbanks located in Northern Italy. The conversion to biogas of feedstocks is greatly influenced by the composition of the organic matter, content of cellulose, and lignin in particular. The production of biomass per hectare and the consequent biogas production were also evaluated. The experimental tests were performed on both samples of fresh grass in laboratory scale batch reactors, characterized by 4.0 L of volume and operated in mesophilic conditions (38 • C), for 40 days per cycle. The anaerobic digestion process was performed on a mixture of inoculum and grass, characterized by inoculum:substrate VS (volatile solids) ratio equal to 2. The inoculum was represented by digestate from a full-scale anaerobic digestion plant fed with dairy cow manure. The results in terms of biogas production, biogas quality (CH 4 , CO 2 , H 2 S), and emissions from digestates (NH 3 , CO 2 and CH 4) are presented in the paper. Total solids (TS), volatile solids (VS), pH, volatile fatty acids (VFA), alkalinity, acidity vs. alkalinity ratio, fibers (cellulose, lignin), and total Kjieldahl nitrogen (TKN) were determined both on input and output of the process. The biogas yield obtained from grass resulted higher than expected, quite similar to the yield obtained from energy crops, with Biomethane Potential (BMP) of 340.2 NL•kg −1 VS and of 307.7 NL•kg −1 VS, respectively, for spring and summer grass. Biogas quality was slightly lower for summer grass, perhaps in relation to the higher content of fibers (lignin). Alternatively, the yield of grass per surface was significantly different between spring and summer with the highest production in the summer. In fact, the results revealed a methane yield of 263 Nm 3 •ha −1 and of 1181 Nm 3 •ha −1 , respectively for spring and summer grass.
BIOGAS PRODUCTION FROM MAIZE AND CLOVER GRASS ESTIMATED WITH THE METHANE ENERGY VALUE SYSTEM
A world wide increasing demand can be observed to use energy crops for biogas production. The research project aimed at optimising anaerobic digestion of maize and clover grass. With energy crops, a maximum methane yield per hectare should be achieved. Influence of variety and harvesting time on the methane yield was investigated. Maximum methane yield from late ripening maize varieties ranged between 7100 and 9000 Nm 3 CH 4 ha -1 . Early and medium ripening varieties yielded 5300 -8500 Nm 3 CH 4 ha -1 when grown in favourable regions. On medium to good locations, clover grass yielded 3000 -4500 Nm 3 CH 4 ha -1 . Maize and clover grass are optimally harvested, when the product from specific methane yield and VS yield per hectare reaches a maximum. From the digestion experiments, the new Methane Energy Value System was developed. It estimates the methane yield from the nutrient composition of maize and clover grass silage.
Renewable Energy, 2014
Grassland biomass is likely to be harvested and stored as silage to ensure a predictable quality and a constant supply of feedstock to an anaerobic digestion facility. Grass (Phleum pratense L. var. Erecta) was ensiled following the application of one of six contrasting additive treatments or a 6 h wilt treatment to investigate the effects of contrasting silage fermentation characteristics on CH 4 yield. In general, silage fermentation characteristics had relatively little effect on specific CH 4 yield (from 344 to 383 Nl CH 4 kg À1 volatile solids). However, the high concentrations of fermentation products such as ethanol and butyric acid following clostridial and heterofermentative lactic acid bacterial fermentations resulted in a numerically higher specific CH 4 yield. While the latter fermentation products of undesirable microbial activity have the potential to enhance specific CH 4 yield, the numerically higher specific CH 4 yield may not compensate for the associated total solids and energy losses during ensiling.
Biogas and Methane Yield from Rye Grass
Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2015
Biogas production in the Czech Republic has expanded substantially, including marginal regions for maize cultivation. Therefore, there are increasingly sought materials that could partially replace maize silage, as a basic feedstock, while secure both biogas production and its quality.Two samples of rye grass (Lolium multiflorum var. westerwoldicum) silage with different solids content 21% and 15% were measured for biogas and methane yield. Rye grass silage with solid content of 15% reached an average specific biogas yield 0.431 m3·kg−1 of organic dry matter and an average specific methane yield 0.249 m3·kg−1 of organic dry matter. Rye grass silage with solid content 21% reached an average specific biogas yield 0.654 m3·kg−1 of organic dry matter and an average specific methane yield 0.399 m3·kg−1 of organic dry matter.
Grass Silage for Biogas Production
Advances in Silage Production and Utilization, 2016
Renewable energy resources of part of the Asian region are not only able to fight against climate change issues but also could contribute to economic growth, employment, and energy safety. Biogas production and use are generally regarded as a sustainable practice that can guarantee high greenhouse gas savings. Thailand is an agricultural area suitable for growing of many plants, especially annual crops that can be used as an energy crop or raw material for biogas plant. In addition, grassland biomass is suitable in numerous ways for producing energy and is the most common material for producing biogas in the present scenario. There are several types of grasses popularly growing in Thailand. Grasses are converted to silage which will be used as feedstock for anaerobic digestion. Consequently, this chapter addresses the advances in silage preparations and utilization for efficient biogas production with several digestion methods including dry and wet fermentation processes, monodigestions, and codigestions.