Environmental impact and economic sustainability analysis of a novel anaerobic digestion waste-to-energy pilot plant in Pakistan.

A novel medium-large industrial-scale, anaerobic digestion (AD) waste-to-energy pilot plant has been investigated in terms of cost-benefit, environmental impact, and economic sustainability. This pilot plant exclusively features a multi-digester AD system induced by motorized stirring, methane purification, compression, storage and digestate-fertilizer processing systems, and subsequent electricity generation. The operational productivity and success of the pilot plant has been proven on a variety of waste feedstock substrates in the form of cow-buffalo manure and potato waste. The plant has an average energy productivity of 384 kWh/day and an annual rate of return was estimated to be 15.4%. The life cycle environmental impact analysis deliberated the significant impact potentials in terms of climate change (kg CO2 equivalent), and fossil depletion (kg of oil equivalent) for three selected substrates: 100% cow-buffalo manure (CBM), 100% potato waste (PW), and a mixture of 75% CBM and 25% PW. The results show the climate change potential of 70 kg, 71 kg, and 149 kg and fossil depletion potential of - 2.43 kg, - 16.45 kg, and 18 kg per 2000 kg of substrate slurry, respectively. As such, the substrate of 100% CBM posed the least climate change impacts whereas 100% PW has been established most effective under the fossil depletion category.

Ecological risk assessment of an open dumping site at Mehmood Booti Lahore, Pakistan.

A robust risk assessment of Mehmood Booting Open Dumping (MBOD) site has been carried out by developing holistic risk assessment framework. Framework mainly comprises on baseline study, hazard identification, and risk quantification and evaluation. Physico-chemical analysis of groundwater and leachate, health risk assessment, and estimation of gas emissions from the site were carried out for risk evaluation. LandGEM 3.02 modelling software was used to measure the gas emissions. Analysis of leachate showed that all parameters were exceeding the WHO standard limit. Water samples were found polluted with heavy metals and total coliform contamination. Health survey inferred that problems which were faced by the majority of respondents were respiratory problems (80%). LandGEM model estimated that total landfill gas (TLG) emitted from the site for the year 2014 was 1.760E+05 Mg/year, CH4 emission was 5.445E+06 Mg/year, CO2 emission was 1.290E+05 Mg/year and for non-methane organic compound emission was 2.021E+03 Mg/year. It can be concluded that in the near future, almost all the water locations are possibly threatened with leachate contamination due to the continued accumulation of solid waste at MBOD site. The study recommends that new sanitary landfill sites should be designed to minimize the adverse effects associated with solid waste disposal and to preclude further pollution to surface water, groundwater, soil, and air.