Life cycle environmental impacts of generating electricity and heat from biogas produced by anaerobic digestion

AbstractFinancial incentives in many European countries have led to a surge in anaerobic digestion (AD) installations to produce heat and/or electricity from biogas. This paper presents the life cycle environmental impacts of a system producing biogas from agricultural wastes by AD and co-generating heat and electricity in a combined heat and power (CHP) plant. The results suggest that this can lead to significant reductions in most impacts compared to fossil-fuel alternatives, including the global warming potential (GWP) which can be reduced by up to 50%. However, the acidification and eutrophication potentials are respectively 25 and 12 times higher than for natural gas CHP. The impacts are influenced by the type and source of feedstock, digestate storage and its application on land. Using energy crops such as maize instead of waste reduces the GWP owing to higher biogas yields, but eight out of 11 impacts increase compared to using waste feedstocks. If digestate is not used to displace artificial fertilisers, the majority of impacts are higher than from natural gas CHP. Some other bioenergy options have lower GWP than energy from biogas, including woodchip CHP plants. Implications for policy are discussed based on the results of the study

Sustainability of UK shale gas in comparison with other electricity options: Current situation and future scenarios.

Many countries are considering exploitation of shale gas but its overall sustainability is currently unclear. Previous studies focused mainly on environmental aspects of shale gas, largely in the US, with scant information on socio-economic aspects. To address this knowledge gap, this paper integrates for the first time environmental, economic and social aspects of shale gas to evaluate its overall sustainability. The focus is on the UK which is on the cusp of developing a shale gas industry. Shale gas is compared to other electricity options for the current situation and future scenarios up to the year 2030 to investigate whether it can contribute towards a more sustainable electricity mix in the UK. The results obtained through multi-criteria decision analysis suggest that, when equal importance is assumed for each of the three sustainability aspects shale gas ranks seventh out of nine electricity options, with wind and solar PV being the best and coal the worst options. However, it outranks biomass and hydropower. Changing the importance of the sustainability aspects widely, the ranking of shale gas ranges between fourth and eighth. For shale gas to become the most sustainable option of those assessed, large improvements would be needed, including a 329-fold reduction in environmental impacts and 16 times higher employment, along with simultaneous large changes (up to 10,000 times) in the importance assigned to each criterion. Similar changes would be needed if it were to be comparable to conventional or liquefied natural gas, biomass, nuclear or hydropower. The results also suggest that a future electricity mix (2030) would be more sustainable with a lower rather than a higher share of shale gas. These results serve to inform UK policy makers, industry and non-governmental organisations. They will also be of interest to other countries considering exploitation of shale gas

Investigating the importance of motivations and barriers related to microgeneration uptake in the UK

AbstractMicrogeneration technologies such as solar photovoltaics, solar thermal, wind and heat pumps may be able to contribute to meeting UK climate change and energy security targets, but their contribution to UK domestic energy supply remains low. This research uses a best-worst scaling survey of microgeneration adopters, considerers and rejecters (n=291) to determine the relative importance of different motivations and barriers in microgeneration (non) adoption decisions. The most important motivations are earning money from installation, increasing household energy independence and protecting against future high energy costs. Results indicate that the introduction of Feed-in Tariffs has clearly encouraged a new, more financially-motivated, group to install. Financial factors are the most important barriers and of most importance to rejecters is the prospect of losing money if they moved home. The Green Deal was introduced to reduce this barrier, but may instead exacerbate the problem as potential homebuyers are put off purchasing a home with an attached Green Deal debt. The difficulty in finding trustworthy information on microgeneration is also a major obstacle to adoption, particularly for considerers, despite efforts by the government and microgeneration interest groups to reduce this barrier. Self-sufficiency in energy is a more important motivation for those considering or having rejected installation than for adopters. Provision of accessible information and greater emphasis on household self-sufficiency in energy could help improve the uptake

Energy self-sufficiency, grid demand variability and consumer costs: Integrating solar PV, Stirling engine CHP and battery storage

Global uptake of solar PV has risen significantly over the past four years, motivated by increased economic feasibility and the desire for electricity self-sufficiency. However, significant uptake of solar PV could cause grid balancing issues. A system comprising Stirling engine combined heat and power, solar PV and battery storage (SECHP-PV-battery) may further improve self-sufficiency, satisfying both heat and electricity demand as well as mitigating potential negative grid effects. This paper presents the results of a simulation of 30 households with different energy demand profiles using this system, in order to determine: the degree of household electricity self-sufficiency achieved; resultant grid demand profiles; and the consumer economic costs and benefits. The results indicate that, even though PV and SECHP collectively produced 30% more electricity than the average demand of 3300. kWh/yr, households still had to import 28% of their electricity demand from the grid with a 6. kWh battery. This work shows that SECHP is much more effective in increasing self-sufficiency than PV, with the households consuming on average 49% of electricity generated (not including battery contribution), compared to 28% for PV. The addition of a 6. kWh battery to PV and SECHP improves the grid demand profile by 28% in terms of grid demand ramp-up requirement and 40% for ramp-downs. However, the variability of the grid demand profile is still greater than for the conventional system comprising a standard gas boiler and electricity from the grid. These moderate improvements must be weighed against the consumer cost: with current incentives, the system is only financially beneficial for households with high electricity demand (<4300. kWh/yr). A capital grant of 24% of the installed cost of the whole micro-generation system is required to make the system financially viable for households with an average electricity demand (3300. kWh/yr)

Evaluation of environmental impacts in the catering sector: the case of pasta

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Environmental implications of decarbonising electricity supply in large economies: The case of Mexico

AbstractDriven by the security of supply and climate change concerns, decarbonisation of energy supply has become a priority for many countries. This study focuses on Mexico, the world’s 14th largest economy, and considers the environmental implications of decarbonising its electricity supply. Eleven scenarios are considered for the year 2050 with different technology mixes and GHG reduction targets, ranging from stabilisation at the year 2000 level to a reduction of 60–85%. Unlike most energy scenario analyses which focus mainly on direct CO2 or GHG emissions, this paper presents the full life cycle impacts of electricity generation in 2050 considering ten environmental impacts which, in addition to global warming, include resource and ozone layer depletion, acidification, eutrophication, summer smog, human and eco-toxicity. The results indicate that continuing with business as usual (BAU) would double the current life cycle GHG emissions, even if annual electricity demand growth was reduced to 2.25% from the current 2.8%. Switching from the current fossil fuel mix to a higher contribution of renewables (55–86%) and nuclear power (up to 30%) would lead to a significant reduction of all ten life cycle impacts compared to the current situation and up to an 80% reduction compared to BAU

Towards sustainable production and consumption: A novel DEcision-Support Framework IntegRating Economic, Environmental and Social Sustainability (DESIRES)

AbstractThe idea of sustainable production and consumption is becoming a widely-accepted societal goal worldwide. However, its implementation is slow and the world continues to speed down an unsustainable path. One of the difficulties is the sheer complexity of production and consumption systems that would need to be re-engineered in a more sustainable way as well as the number of sustainability constraints that have to be considered and satisfied simultaneously. This paper argues that bringing about sustainable production and consumption requires a systems approach underpinned by life cycle thinking as well as an integration of economic, environmental and social aspects. In an attempt to aid this process, a novel decision-support framework DESIRES has been developed comprising a suite of tools, including scenario analysis, life cycle costing, life cycle assessment, social sustainability assessment, system optimisation and multi-attribute decision analysis. An application of the framework is illustrated by a case study related to energy