• Energy Research

AbstractThis article identifies marginal land technically available for the production of energy crops in China, compares three models of yield prediction forMiscanthus × giganteus,Panicum virgatumL.(switchgrass), andJatropha, and estimates their spatially specific yields and technical potential for 2017. Geographic Information System (GIS) analysis of land use maps estimated that 185 Mha of marginal land was technically available for energy crops in China without using areas currently used for food production. Modeled yields were projected forMiscanthus × giganteus, a GIS‐based Environmental Policy Integrated Climate model for switchgrass and Global Agro‐Ecological Zone model forJatropha. GIS analysis and MiscanFor estimated more than 120 Mha marginal land was technically available forMiscanthuswith a total potential of 1,761 dry weight metric million tonne (DW Mt)/year. A total of 284 DW Mt/year of switchgrass could be obtained from 30 Mha marginal land, with an average yield of 9.5 DW t ha−1 year−1. More than 35 Mha marginal land was technically available forJatropha, delivering 9.7 Mt/year ofJatrophaseed. The total technical potential from available marginal land was calculated as 31.7 EJ/year forMiscanthus, 5.1 EJ/year for switchgrass, and 0.13 EJ/year forJatropha. A total technical bioenergy potential of 34.4 EJ/year was calculated by identifying best suited crop for each 1 km2grid cell based on the highest energy value among the three crops. The results indicate that the technical potential per hectare ofJatrophais unable to compete with that of the other two crops in each grid cell. This modeling study provides planners with spatial overviews that demonstrate the potential of these crops and where biomass production could be potentially distributed in China which needs field trials to test model assumptions and build experience necessary to translate into practicality.

AbstractBioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO2, N2O and CH4 during crop production may reduce or completely counterbalance CO2 savings of the substituted fossil fuels. These greenhouse gases (GHGs) need to be included into the carbon footprint calculation of different bioenergy crops under a range of soil conditions and management practices. This review compiles existing knowledge on agronomic and environmental constraints and GHG balances of the major European bioenergy crops, although it focuses on dedicated perennial crops such as Miscanthus and short rotation coppice species. Such second‐generation crops account for only 3% of the current European bioenergy production, but field data suggest they emit 40% to >99% less N2O than conventional annual crops. This is a result of lower fertilizer requirements as well as a higher N‐use efficiency, due to effective N‐recycling. Perennial energy crops have the potential to sequester additional carbon in soil biomass if established on former cropland (0.44 Mg soil C ha−1 yr−1 for poplar and willow and 0.66 Mg soil C ha−1 yr−1 for Miscanthus). However, there was no positive or even negative effects on the C balance if energy crops are established on former grassland. Increased bioenergy production may also result in direct and indirect land‐use changes with potential high C losses when native vegetation is converted to annual crops. Although dedicated perennial energy crops have a high potential to improve the GHG balance of bioenergy production, several agronomic and economic constraints still have to be overcome.

AbstractThe UK sixth carbon budget has recommended domestic biomass supply should increase to meet growing demand, planting a minimum of 30,000 hectares of perennial energy crops a year by 2035, with a view to establishing 700,000 hectares by 2050 to meet the requirements of the balanced net zero pathway. Miscanthus is a key biomass crop to scale up domestic biomass production in the United Kingdom. A cohesive land management strategy, based on robust evidence, will be required to ensure upscaling of miscanthus cultivation maximizes the environmental and economic benefits and minimizes undesirable consequences. This review examines research into available land areas, environmental impacts, barriers to uptake, and the challenges, benefits, and trade‐offs required to upscale miscanthus production on arable land and grassland in the United Kingdom. Expansion of perennial biomass crops has been considered best restricted to marginal land, less suited to food production. The review identifies a trade‐off between avoiding competition with food production and a risk of encroaching on areas containing high‐biodiversity or high‐carbon stocks, such as semi‐natural grasslands. If areas of land suitable for food production are needed to produce the biomass required for emission reduction, the review indicates there are multiple strategies for miscanthus to complement long‐term food security rather than compete with it. On arable land, a miscanthus rotation with a cycle length of 10–20 years can be employed as fallow period for fields experiencing yield decline, soil fatigue, or persistent weed problems. On improved grassland areas, miscanthus presents an option for diversification, flood mitigation, and water quality improvement. Strategies need to be developed to integrate miscanthus into farming systems in a way that is profitable, sensitive to local demand, climate, and geography, and complements rather than competes with food production by increasing overall farm profitability and resilience.

The Loess Plateau, with a large area of marginal land, holds the potential to produce 62–106 Tg per year of switchgrass biomass; however, the economic feasibility of producing bioenergy in the region is unclear. The farm-gate feedstock production (FGFP) cost of switchgrass was calculated in a spatially explicit way by taking the geographic variation in crop yield, soil properties, land quality, and input costs into consideration in order to evaluate the economic performance of bioenergy production. Cost–supply curves were constructed to explore the energy supply potential of switchgrass feedstock. The calculations were conducted using ArcGIS in a 1 km grid and all the evaluations were conducted under different agricultural management practice (AMP) scenarios in parallel. The FGFP costs showed significant spatial variation ranging from 95 to 7373 CNY (Chinese Yuan) per tonne−1 and that the most economically desirable areas are scattered in the south and southeast region. The weighted average FGFP costs are 710, 1125, and 1596 CNY per tonne−1 for small bale (SB), large bale (LB), and chipping (CP) harvest methods, respectively. The projected energy supply potential is 1927 PJ (Petajoules) per year−1, of which 30–93% can be supplied below the market prices of different fossil fuels according to feedstock formats. Compared to current biomass residual pricing, 50–66 Tg (Teragrams) switchgrass feedstock is competitive. The results demonstrated that the Loess Plateau holds the potential to produce bioenergy that is economically feasible. This study provides a methodological framework for spatially explicit evaluation of the economic performance of perennial energy crops. Detailed information obtained from this study can be used to select the optimal locations and AMPs to produce feedstock production at minimum cost.

Electric trains (ETs) and hydrogen trains (HTs) offer an opportunity for both Japan and the UK to meet their national targets as part of the Paris Agreement. Although ETs and HTs are considered zero emission at the point of use, their true environmental impact is dependent upon non-tailpipe emissions from fuel/energy production and vehicle manufacture, maintenance and disposal. To assess and compare the carbon dioxide emissions produced from ETs and HTs in Japan and the UK from 2020 and 2050, the operating emissions of these trains were projected. Results compared ET and HT emissions with diesel fuelled trains (DFTs) to better assess which fuel type was the most environmentally friendly. Emissions per train, cumulative emissions and total energy required for ETs and HTs were compared.Results indicated that even with technological improvements, DD DFTs produced the highest level of emissions in both countries, followed by HTs. Although ETs produced the lowest level of emissions, it is likely that a mix of both ETs and HTs will be required to meet passenger demand and for travel within rural areas. As Japan has already transitioned towards ETs, future policy focus should be placed on decarbonisation of their energy sector and a shift away from fossil fuels in favour of renewable energy, otherwise environmental benefits of ETs will be diminished. As the UK is decarbonising its electricity network, focus needs to be placed on electrifying the majority of the rail network and running the rest on hydrogen to decarbonise rail transport.

This paper investigates the expansion of electric cars and their impact on the environment and the user; assuming a future scenario where all of the light-duty vehicles that use an internal combustion engine will be replaced by electric cars in Scotland. The idea is to investigate the impact on the environment and the financial effect on the user. The methodology is based on analysing the most common electric and conventional vehicles to estimate the amount of additional electricity that would be needed to charge that expansion. The paper has also looked at the running costs. The results show that approximately 4 GWh per annum of additional electricity will be needed to compensate for such growth in electricity demand. With the rise in electricity production, the amount of carbon emissions from the electrical grid is expected to increase slightly by 0.47 megatons CO2 per annum. Given that the carbon dioxide generated by the light internal combustion vehicles at the moment is 3.6 megatons of CO2 per year, it is concluded that the total amount of greenhouse gases from the electricity grid will decrease by circa 33.7% if all conventional cars in Scotland are replaced by electric cars. The initial cost of an electric car is found to be higher than conventional diesel or petrol one, but in the long term, the cost to power an electric vehicle is expected to be much cheaper. However, electric cars still have their own drawbacks as they need significant time to be charged, and will consume significant energy for heating the interior and windscreens to prevent condensation in cold weather leading to an estimated reduction in range of approximately 28% in some situations.