Abdul-Sattar Nizami

Key issues in life cycle assessment of ethanol production from lignocellulosic biomass: challenges and perspectives.

Progressive depletion of conventional fossil fuels with increasing energy consumption and greenhouse gas (GHG) emissions have led to a move towards renewable and sustainable energy sources. Lignocellulosic biomass is available in massive quantities and provides enormous potential for bioethanol production. However, to ascertain optimal biofuel strategies, it is necessary to take into account environmental impacts from cradle to grave. Life cycle assessment (LCA) techniques allow detailed analysis of material and energy fluxes on regional and global scales. This includes indirect inputs to the production process and associated wastes and emissions, and the downstream fate of products in the future. At the same time if not used properly, LCA can lead to incorrect and inappropriate actions on the part of industry and/or policy makers. This paper aims to list key issues for quantifying the use of resources and releases to the environment associated with the entire life cycle of lignocellulosic bioethanol production.

Review of the integrated process for the production of grass biomethane.

Production of grass biomethane is an integrated process which involves numerous stages with numerous permutations. The grass grown can be of numerous species, and it can involve numerous cuts. The lignocellulosic content of grass increases with maturity of grass; the first cut offers more methane potential than the later cuts. Water-soluble carbohydrates (WSC) are higher (and as such methane potential is higher) for grass cut in the afternoon as opposed to that cut in the morning. The method of ensiling has a significant effect on the dry solids content of the grass silage. Pit or clamp silage in southern Germany and Austria has a solids content of about 40%; warm dry summers allow wilting of the grass before ensiling. In temperate oceanic climates like Ireland, pit silage has a solids content of about 21% while bale silage has a solids content of 32%. Biogas production is related to mass of volatile solids rather than mass of silage; typically one ton of volatile solid produces 300 m(3) of methane. The dry solids content of the silage has a significant impact on the biodigester configuration. Silage with a high solids content would lend itself to a two-stage process; a leach bed where volatile solids are converted to a leachate high in chemical oxygen demand (COD), followed by an upflow anaerobic sludge blanket where the COD can be converted efficiently to CH(4). Alternative configurations include wet continuous processes such as the ubiquitous continuously stirred tank reactor; this necessitates significant dilution of the feedstock to effect a solids content of 12%. Various pretreatment methods may be employed especially if the hydrolytic step is separated from the methanogenic step. Size reduction, thermal, and enzymatic methodologies are used. Good digester design is to seek to emulate the cow, thus rumen fluid offers great potential for hydrolysis.

Key issues in estimating energy and greenhouse gas savings of biofuels: challenges and perspectives

The increasing demand for biofuels has encouraged the researchers and policy makers worldwide to find sustainable biofuel production systems in accordance with the regional conditions and needs. The sustainability of a biofuel production system includes energy and greenhouse gas (GHG) saving along with environmental and social acceptability. Life cycle assessment (LCA) is an internationally recognized tool for determining the sustainability of biofuels. LCA includes goal and scope, life cycle inventory, life cycle impact assessment, and interpretation as major steps. LCA results vary significantly, if there are any variations in performing these steps. For instance, biofuel producing feedstocks have different environmental values that lead to different GHG emission savings and energy balances. Similarly, land-use and land-use changes may overestimate biofuel sustainability. This study aims to examine various biofuel production systems for their GHG savings and energy balances, relative to conventional fossil fuels with an ambition to address the challenges and to offer future directions for LCA based biofuel studies. Environmental and social acceptability of biofuel production is the key factor in developing biofuel support policies. Higher GHG emission saving and energy balance of biofuel can be achieved, if biomass yield is high, and ecologically sustainable biomass or non-food biomass is converted into biofuel and used efficiently.

Optimizing the operation of a two-phase anaerobic digestion system digesting grass silage.

This paper examines the optimization of an existing two-phase anaerobic digestion process using grass silage as a feedstock. The system comprises 6 leach beds connected to an upflow anaerobic sludge blanket (UASB). The existing system produced 305 L CH(4) kg(-1) VS added at an overall retention time of 42 days (6 leach beds emptied and fed sequentially every 7 days in series). The desired improvements were a reduction in retention time with increased methane production. It was noted in the existing system that biogas production and COD levels fell off in the last 2 days of each 7-day cycle. Thus the first change involved reduction in retention time to 30 days (6 leach beds fed sequentially every 5 days in series). This lead to a slight improvement in methane production (310 L CH(4) kg(-1) VS added). The second change was effected by separation of flows to the first stage (leach beds) and the second stage (UASB) through addition of an extra pump to optimize leaching. This led to an increase in CH(4) production (341 L CH(4) kg(-1) VS). The overall improvement from the existing system was an increase of 11.8% in methane production and a reduction in size or retention time of 40% (42 days decreased to 30 days retention time).

Waste biorefineries : Enabling circular economies in developing countries

This paper aims to examine the potential of waste biorefineries in developing countries as a solution to current waste disposal problems and as facilities to produce fuels, power, heat, and value-added products. The waste in developing countries represents a significant source of biomass, recycled materials, chemicals, energy, and revenue if wisely managed and used as a potential feedstock in various biorefinery technologies such as fermentation, anaerobic digestion (AD), pyrolysis, incineration, and gasification. However, the selection or integration of biorefinery technologies in any developing country should be based on its waste characterization. Waste biorefineries if developed in developing countries could provide energy generation, land savings, new businesses and consequent job creation, savings of landfills costs, GHG emissions reduction, and savings of natural resources of land, soil, and groundwater. The challenges in route to successful implementation of biorefinery concept in the developing countries are also presented using life cycle assessment (LCA) studies.

Waste-to-energy and recycling value for developing integrated solid waste management plan in Lahore

ABSTRACT This paper aims to determine the waste-to-energy (WTE) and recycling value of municipal solid waste (MSW) for developing an integrated solid waste management (ISWM) system for Lahore, the second largest city in Pakistan. The overall generated waste in Lahore contains 58% organic waste, 25% recyclables, and 17% others. The recyclable materials including glass, paper, and plastic are generating US

Influence of temperature and reaction time on the conversion of polystyrene waste to pyrolysis liquid oil

15.3 million per year mostly by informal sector. An estimated production of 0.45 m3 CH4/kg volatile solids with total energy value of 8747.3 TJ or 2.43 TWh can be achieved if the total organic waste stream (0.57 million ton/year) dumped at Saggian landfill site is processed using anaerobic digestion technology. The estimated refused derived fuel (RDF) value for MSW, excluding metals, glass, and other inorganic waste is about 7.71 MJ/kg with total energy potential of 6191.13 TJ or 1.72 TWh/year. The presence of high volatile organic carbon and fixed carbon in textile and paper-related waste confirmed their suitability for incineration process. A significant reduction in the final volume of waste reaching to landfill can be achieved if these WTE technologies and recycling practices are in place. This will make a premise for ISWM system in Lahore based on reduce, reuse, recycle, and recovery principles. The recovered materials and energy will not only generate revenue to fund waste management activities in Lahore, but also protect the River Ravi from waste pollution.

Analysis of Physiochemical Parameters to Evaluate the Drinking Water Quality in the State of Perak, Malaysia

This paper aims to investigate the effect of temperature and reaction time on the yield and quality of liquid oil produced from a pyrolysis process. Polystyrene (PS) type plastic waste was used as a feedstock in a small pilot scale batch pyrolysis reactor. At 400°C with a reaction time of 75min, the gas yield was 8% by mass, the char yield was 16% by mass, while the liquid oil yield was 76% by mass. Raising the temperature to 450°C increased the gas production to 13% by mass, reduced the char production to 6.2% and increased the liquid oil yield to 80.8% by mass. The optimum temperature and reaction time was found to be 450°C and 75min. The liquid oil at optimum conditions had a dynamic viscosity of 1.77mPas, kinematic viscosity of 1.92cSt, a density of 0.92g/cm3, a pour point of -60°C, a freezing point of -64°C, a flash point of 30.2°C and a high heating value (HHV) of 41.6MJ/kg this is similar to conventional diesel. The gas chromatography with mass spectrophotometry (GC-MS) analysis showed that liquid oil contains mainly styrene (48%), toluene (26%) and ethyl-benzene (21%) compounds.

Evaluation of natural gas hydrates as a future methane source

The drinking water quality was investigated in suspected parts of Perak state, Malaysia, to ensure the continuous supply of clean and safe drinking water for the public health protection. In this regard, a detailed physical and chemical analysis of drinking water samples was carried out in different residential and commercial areas of the state. A number of parameters such as pH, turbidity, conductivity, total suspended solids (TSS), total dissolved solids (TDS), and heavy metals such as Cu, Zn, Mg, Fe, Cd, Pb, Cr, As, Hg, and Sn were analysed for each water sample collected during winter and summer periods. The obtained values of each parameter were compared with the standard values set by the World Health Organization (WHO) and local standards such as National Drinking Water Quality Standard (NDWQS). The values of each parameter were found to be within the safe limits set by the WHO and NDWQS. Overall, the water from all the locations was found to be safe as drinking water. However, it is also important to investigate other potential water contaminations such as chemicals and microbial and radiological materials for a longer period of time, including human body fluids, in order to assess the overall water quality of Perak state.

Optimizing the thermophilic hydrolysis of grass silage in a two-phase anaerobic digestion system

ABSTRACT In recent years, attention has been given to obtaining methane gas from natural gas hydrates (NGHs) sediment; but its production, economics, and safety are still far away from being commercially viable for many years, and so more research is needed. NGHs are nonstoichiometric crystalline solid compounds that form from mixtures of water molecules and light weight natural gases such as methane, ethane, propane, and carbon dioxide. They are formed in specific thermodynamic conditions, low temperatures (5–15°C) and high pressures (2–3 MPa), and are found in (a) onshore polar regions beneath permafrost and (b) offshore deep-sea sediments. Methane, NG, is the cleanest fossil fuel and its huge amounts in NGHs have carbon quantities more than double of all fossil fuels. The methods that have been proposed for NG extraction from NGHs include: (a) depressurization, (b) thermal stimulation, and (c) chemical inhibitor injections. The authors review the potential of methane gas from NGHs as an unconventional source of future energy. The formation of NGHs as well as extraction of methane from NGHs coupled with technical and environmental challenges are also addressed.