How can we improve biomethane production per unit of feedstock in biogas plants?

Biogas production is one of the number of tools that may be used to alleviate the problems of global warming, energy security and waste management. Biogas plants can be difficult to sustain from a financial perspective. The facilities must be financially optimized through use of substrates with high biogas potential, low water content and low retention requirement. This research carried out in laboratory scale batch digesters assessed the biogas potential of energy crops (maize and grass silage) and solid manure fractions from manure separation units. The ultimate methane productivity in terms of volatile solids (VS) was determined as 330, 161, 230, 236, 361 L/kg VS from raw pig slurry, filter pressed manure fiber (FPMF), chemically precipitated manure fiber (CPMF), maize silage and grass silage respectively. Methane productivity based on mass (L/kg substrate) was significantly higher in FPMF (55 L/kg substrate), maize silage (68 L/kg substrate) and grass silage (45–124 L/kg substrate (depending on dry solids of feedstock)) as in comparison to raw pig slurry (10 L/kg substrate). The use of these materials as co-substrates with raw pig slurry will increase significantly the biomethane yield per unit feedstock in the biogas plant.     

Competitive energy markets and nuclear power: Can we have both,do we want either?

In 1987, the UK Conservative Party was re-elected promising to transform the electricity industry into a privatised competitive industry and to promote an expansion of nuclear power. Fulfilling both objectives was not possible. The nuclear plants were withdrawn from the sale and plans to build new plants were abandoned, but privatisation proceeded. In 2007, the Labour government began a new attempt to build nuclear plants to operate in the competitive electricity market, promising that no subsidies would be offered to them. By 2010, the utilities that were planning to build nuclear plants were beginning to suggest that ‘support’ in some form would be needed if they were to build new plants. More surprisingly, the energy regulator, Ofgem, cast doubt on whether a competitive wholesale electricity market would provide security of supply. In 1990, the UK government opted for a competitive electricity market over expanding nuclear power. Now, the option of opting for a competitive electricity market may not exist. However, this might not leave the way open for new nuclear plants. The expected cost of power from new nuclear plants is now so high that no more than one or two heavily subsidised plants will be built.     

Ten years of corporate action on climate change: What do we have to show for it?

A significant proportion of the world's greenhouse gas emissions can be attributed, directly or indirectly, to corporate activities. An increasing number of companies have set targets and have adopted initiatives to reduce their greenhouse gas emissions, raising the question of what sorts of outcomes can realistically be expected from corporate action on climate change? This paper aims to shed some light on this issue through an analysis of the climate change performance of the UK supermarket sector. This sector is directly responsible for around 1% of UK greenhouse gas emissions, but it has been estimated that indirectly it may be responsible for up to 10% of emissions. In the period between 2000 and 2010, the major UK supermarkets transformed their approach to climate change. This paper examines the outcomes that resulted from these actions. It finds that there have been significant and steady improvements in energy efficiency, but that these efficiency gains are often outstripped by the impacts of business growth. For most companies, short of a radical redesign of their business activities, or an expansion of the scope of their energy management initiatives to include their indirect emissions, total greenhouse gas emissions will tend to increase over time.     

An integrated assessment of a large-scale biodiesel production in Italy: Killing several birds with one stone?

Biofuels are often presented as a contribution towards the solution of the problems related to our strong dependency on fossil fuels, i.e. greenhouse effect, energy dependency, urban pollution, besides being a way to support rural development. In this paper, an integrated assessment approach is employed to discuss the social desirability of a large-scale biodiesel production in Italy, taking into account social, environmental and economic factors. The conclusion is that the advantages in terms of reduction of greenhouse gas emissions, energy dependency and urban pollution would be very modest. The small benefits would not be enough to offset the huge costs in terms of land requirement: if the target of the European Directive 2003/30/EC were reached (5.75% of the energy used for transport by 2010) the equivalent of about one-third of the Italian agricultural land would be needed. The consequences would be a considerable increase in food imports and large environmental impacts in the agricultural phase. Also, since biodiesel must be de-taxed in order to make it competitive with oil-derived diesel, the Italian energy revenues would be reduced. In the end, rural development remains the only sound reason to promote biodiesel, but even for this objective other strategies look more advisable, like supporting organic agriculture.     

Where do all the windmills go? Influence of the institutional setting on the spatial distribution of renewable energy installation

Promoting renewable energy sources is one policy response to climate change. Not only is there currently a debate over the best policy instrument, it is also discussed whether the renewable energy production should be expanded centralized at locations with the highest production potential or decentralized close to load. It is yet not fully understood what influences the spatial distribution of renewable energy installation.I assess the effect of subsidy scheme and market design on the spatial distribution of wind energy installations by comparing (a) feed-in tariffs versus market premiums and (b) uniform versus nodal pricing. The analysis is based on theoretical considerations and using a six-node test model that reflects the consumption and renewable resource distribution in several countries and regions.The institutional setting has great influence on the spatial distribution and resulting system costs. With uniform pricing, a market premium only leads to a more decentralized expansion of renewable energy production than a tariff when sites share similar wind conditions. Spatially more distributed expansion of wind power performs better in terms of total costs and share of wind power in final demand when networks are restricted.     

Does the production of Belgian bioethanol fit with European requirements on GHG emissions? Case of wheat

This paper undertakes an environmental evaluation of bioethanol production, using wheat cultivated in Belgium. Cultivation steps are modelled using Belgian specific data. Wheat transformation in ethanol relies on industrial data. GHG emissions of the whole life cycle are calculated and compared with the default values given by the European Renewable Energy Directive. Belgian wheat bioethanol achieves a 5% higher GHG reduction than the one mentioned in the European directive but impact repartition is different with a higher importance of cultivation step in our case. Belgian wheat bioethanol complies with the current sustainability criteria but is also able to conform to further ones. Sensitivity analyses are performed on the importance of N fertilizers and associated emissions known as main important parameters. These analyses reveal non negligible variations and then a range of available GHG reduction when using wheat bioethanol.     

Biofuels Bonanza?: Exploring community perceptions of the promises and perils of biofuels production

While the expansion of the biofuels industry has received scholarly attention with respect to environmental and food security concerns, little research has explored the impacts of biofuels industry on local communities where ethanol plants are located. Drawing on sociology of networks and flows theory to situate expansion of the industry globally, this paper uses a community case study approach to examine local community perceptions of benefits and burdens of the ethanol industry. Data from community level surveys, individual and focus group interviews in three case study communities in Iowa and Kansas in the Midwestern region of the United States are utilized to explore community perceptions. Results show that community members believe that ethanol plants have brought modest economic benefits to their community. Increased traffic and water competition were two areas of concern identified by residents with respect to local ethanol plants, but other environmental impacts were not prominently identified by community members. Widespread concerns were expressed about future viability of the ethanol industry and the devastating impacts that future declines in the industry would have on communities. This research highlights the social vulnerabilities that place-bound communities in biofuels regions are experiencing.     

Investment in energy efficiency: do the characteristics of investments matter?

??Investment in energy efficiency: do the characteristics of firms matter??? In their famous 1998 paper, DeCanio and Watkins raised the question and answered it affirmatively. Our paper addresses a parallel question: ??Investment in energy efficiency: do the characteristics of investments matter??? To answer this question, we first describe our new investment decision-making model, applicable to all investment types. We then discuss our research results, based on questionnaires submitted to finance managers of 35 major electricity consumers in various commercial and industrial sectors. We show how characteristics other than profitability play an important role in investment choices. The investment category influences profitability evaluation, profitability requirement, and, ultimately, the decision made. For half of the firms in our study, energy-efficiency investments did not exist as a category. However, wide diversity regarding investment behavior is observed between firms. Our findings lead to a different explanation of the energy-efficiency gap and open the way for a new approach to promoting energy-efficiency investments, which is briefly discussed in the conclusion.     

Where did the time (series) go? Estimation of marginal emission factors with autoregressive components

This paper offers a novel contribution to the literature on Marginal Emission Factors (MEF) by proposing a robust empirical methodology for their estimation across both time and space. Our Autoregressive Integrated Moving Average models with time-effects not only outperforms the established models in the economics literature but it also proves more reliable than variations adopted in the field of engineering. Utilising half-hourly data on carbon emissions and generation in Great Britain, the results allow us to identify a more stable path of MEFs than obtained with existing methodologies. We also estimate marginal emission effects over subsequent time periods (intra-day), rather than focussing only on individual settlement periods (inter-day). This allows us to evaluate the annual cycle of emissions as a result of changes in the economic and social activity which drives demand. Moreover, the reliability of our approach is further confirmed upon exploring the cross-country context. Indeed, our methodology proves reliable when applied to the case of Italy, which is characterised by a different data generation process. Crucially, we provide a more robust basis for valuing actual carbon emission reductions, especially in electricity systems with high penetration of intermittent renewable technologies.     

Adapting the French nuclear fleet to integrate variable renewable energies via the production of hydrogen: Towards massive production of low carbon hydrogen?

Producing low-carbon hydrogen at a competitive rate is becoming a new challenge with respect to efforts to reduce greenhouse gas emissions. We examine this issue in the French context, which is characterised by a high nuclear share and the target to increase variable renewables by 2050. The goal is to evaluate the extent to which excess nuclear power could contribute to producing low-carbon hydrogen.Our approach involves designing scenarios for nuclear and renewables, modelling and evaluating the potential nuclear hydrogen production volumes and costs, examining the latter through the scope of hydrogen market attractiveness and evaluating the potential of CO₂ mitigation.This article shows that as renewable shares increase, along with the hydrogen market expected growth driven by mobility uses, opportunities are created for the nuclear operator. If nuclear capacities are maintained, nuclear hydrogen production could correspond to the demand by 2030. If not, possibilities could still exist by 2050.     

Techno-economic analysis of processes with integration of fluidized bed heat exchangers for H2 production – Part 2: Chemical-looping combustion

This work covers a techno-economic assessment for processes with inherent CO₂ separation, where a fluidized bed heat exchanger (FBHE) is used as heat source for steam reforming in a hydrogen production plant. This article builds upon the work presented in Part 1 of this study by Stenberg et al. [1], where a process excluding CO₂ capture was examined. Part 2 suggests two process configurations integrating steam reforming with a chemical-looping combustion (CLC) system, thus providing inherent CO₂ capture. The first system (case CM) uses natural gas as supplementary fuel whereas the second system (case CB) uses solid biomass, which enables net negative CO₂ emissions. In both systems, the reformer tubes are immersed in a bubbling fluidized bed where heat for steam reforming is efficiently transferred to the tubes. The processes include CO₂ compression for pipeline transportation, but excludes transport and storage. The CLC system is designed based on key parameters, such as the oxygen carrier circulation rate and oxygen transport capacity. The first system displays a process with net zero emissions and a hydrogen production efficiency which is estimated to 76.2%, which is almost 8% higher than the conventional process. The levelized production cost is 1.6% lower at below 2.6 €/kg H₂. The second system shows the possibility to reduce the emissions to ?34.1 g CO₂/MJ_H2 compared to the conventional plant which emits 80.7 g CO₂/MJ_H2. The hydrogen production efficiency is above 72% and around 2% higher than the conventional process. The capital investments are higher in this plant and the levelized hydrogen production cost is estimated to around 2.67 €/kg. The cost of CO₂ avoidance, based on a reference SMR plant with CO₂ capture, is low for both cases (?4.3 €/ton_CO2 for case CM and 2.7 €/ton_CO2 for case CB).     

Hydrogen production by Escherichia coli growing in different nutrient media with glycerol: Effects of formate,pH, production kinetics and hydrogenases involved

The Escherichia coli BW25113 or MC4100 wild type parental strains growth and H₂ production kinetics was studied in batch cultures of minimal salt medium (MSM) and peptone medium (PM) at pH of 5.5–7.5 upon glycerol (10 g L^?1) fermentation and formate (0.68 g L^?1) supplementation. The role of formate alone or with glycerol on growth and H₂ production via hydrogenases (Hyd) was investigated in double hyaB hybC (lacking large subunits of Hyd 1 and 2), triple hyaB hybC hycE (lacking large subunits of Hyds 1-3) and sole selC (lacking formate dehydrogenase H) mutants during 24 h bacterial growth. H₂ production was delayed and observed after 24 h bacterial wild type strains growth on MSM. Moreover, it reached the maximal values after 72 h growth at the pH 6.5 and pH 7.5. Biomass formation of the mutants used was inhibited ～3.5 fold compared with wild type, and H₂ production was absent in hyaB hybC hycE and selC mutants upon glycerol utilization on MSM at pHs of 5.5–7.5. Formate inhibited bacterial growth on MSM with glycerol, but enhanced and recovered H₂ production by hybC mutant at pH 7.5. H₂ evolution was delayed at pH 7.5 in PM, but observed and stimulated at pH 6.5 upon glycerol and formate utilization in hyaB hybC mutant. H₂ production was absent in hyaB hybC hycE and selC mutants upon glycerol, formate alone or with glycerol fermentation at pH 6.5 and pH 7.5; formate supplementation had no effect. The results point out E. coli ability to grow and utilize glycerol in MSM with comparably high H₂ yield: as well as they suggest the key role of Hyd-3 at both pH 6.5 and pH 7.5 and the role of Hyd-2 and Hyd-4 at pH 7.5 in H₂ production by E. coli during glycerol fermentation with formate supplementation. The results obtained are novel and might be useful in H₂ production biotechnology development using different nutrient media and glycerol and formate as feedstock.     

CFD modeling of hydrogen production using steam reforming of methane in monolith reactors: Surface or volume-base reaction model?

In the present work, two approaches for reaction modeling in monolith reactors were taken into account and compared to each other. In the first approach, the reactions are assumed to take place on the wall surfaces, while penetration and reaction of chemical species inside a thin layer near the walls are of essential concern in the second approach. Experiments of Steam Methane Reforming (SMR) were carried out in a Bench-scale monolith reactor. A single-channel was considered and two axi-symmetric CFD models were developed for modeling. General kinetic models for SMR and Water-Gas-Shift (WGS) reaction rates based on Langmuir-Hinshelwood type were employed. Comparisons between modeling results and experimental data showed that despite its ease of implementation, the first approach (surface reactions) exhibits better results both in generality and accuracy. It was realized that uncertainties in obtaining the effective diffusion coefficients in the volumetric approach may cause a variation up to 16% in the prediction of reaction conversion.     

Australian retail electricity prices: Can we avoid repeating the rising trend of the past?

After a stable or declining real trend that persisted for more than half a century, Australian retail electricity prices have experienced a substantial increase, in real terms, since 2007. This has mainly been driven by increases in the cost of electricity distribution and to a lesser degree in the cost of electricity generation. Reducing greenhouse gas emissions, which is a bipartisan political goal in Australia, will likely deliver further increases in generation costs due to the expected higher cost of low emission technology. Participating in global negotiations on emission reduction targets and designing efficient policy mechanisms have been a major focus of governments over the last several decades. In contrast, managing distribution system costs has received less attention. While there were a number of factors which drove historical increases in distribution costs, management of peak demand growth could help contain or reduce the extent to which consumers, particularly households, experience further increases in distribution costs. The paper demonstrates how different combinations of carbon price and peak demand scenarios could impact future residential and industrial retail electricity prices to 2050 and discusses some behavioural and technological solutions to manage peak demand and potential barriers to their deployment.     

Adoption of solar home lighting systems in India: What might we learn from Karnataka?

Karnataka has been among the most successful markets for solar lighting systems (SLS) among Indian states. In order to understand the dynamics of systems adoption and operation, that have fostered market based adoption of solar lighting, we interviewed rural households from six districts that had purchased solar lighting systems using loans at market rates, the rural banks that provided loans and the solar firms that marketed the technology. We found that a large proportion of households in our sample were connected to the grid but chose to install solar lighting because they considered the power supply from the grid to be unreliable. Households in our sample reported savings on electricity costs and reduced kerosene usage for lighting. In addition to providing credit, banks also play a key role in ensuring good service and maintenance; the viability of the SLS market is thus critically dependent on the role that the banks play as intermediaries between consumers and solar firms in rural areas. Government programs should be carefully designed to match the incentives of firms, banks and consumers if the successes of the ‘Karnataka model’ are to be repeated and amplified.     

A missing link? The case of Norway and Sweden: Does increased renewable energy production impact domestic greenhouse gas emissions?

This article examines how the EU׳s RES directive¹ will impact domestic greenhouse gas emissions in Norway and Sweden by 2020. The directive aims for a higher RES share in the energy consumption mix, and Norway and Sweden have established a common electricity certificate scheme to help achieve these RES goals. In terms of how these two national RES plans will impact domestic emissions by 2020, factors such as nuclear power, consumption changes and the energy balance must be considered. The most practical approach to evaluate the plans’ impact on emissions is to focus on changes in carbon-based consumption within the three directive sectors.The Norwegian RES action plan will not affect domestic emissions unless the electricity surplus generated by the certificate market is used to phase out fossil fuels in domestic sectors beyond the scope of the RES directive. The use of electricity to phase out fossil fuel consumption in the offshore sector would substantially reduce Norwegian emissions figures. The Swedish plan would positively impact Swedish greenhouse gas emissions; however, this impact is limited, primarily because a substantial increase in energy consumption is expected.     

Technology interactions among low-carbon energy technologies: What can we learn from a large number of scenarios?

Advanced low-carbon energy technologies can substantially reduce the cost of stabilizing atmospheric carbon dioxide concentrations. Understanding the interactions between these technologies and their impact on the costs of stabilization can help inform energy policy decisions. Many previous studies have addressed this challenge by exploring a small number of representative scenarios that represent particular combinations of future technology developments. This paper uses a combinatorial approach in which scenarios are created for all combinations of the technology development assumptions that underlie a smaller, representative set of scenarios. We estimate stabilization costs for 768 runs of the Global Change Assessment Model (GCAM), based on 384 different combinations of assumptions about the future performance of technologies and two stabilization goals. Graphical depiction of the distribution of stabilization costs provides first-order insights about the full data set and individual technologies. We apply a formal scenario discovery method to obtain more nuanced insights about the combinations of technology assumptions most strongly associated with high-cost outcomes. Many of the fundamental insights from traditional representative scenario analysis still hold under this comprehensive combinatorial analysis. For example, the importance of carbon capture and storage (CCS) and the substitution effect among supply technologies are consistently demonstrated. The results also provide more clarity regarding insights not easily demonstrated through representative scenario analysis. For example, they show more clearly how certain supply technologies can provide a hedge against high stabilization costs, and that aggregate end-use efficiency improvements deliver relatively consistent stabilization cost reductions. Furthermore, the results indicate that a lack of CCS options combined with lower technological advances in the buildings sector or the transportation sector is the most powerful predictor of high-cost scenarios.     

Is energy cropping in Europe compatible with biodiversity? – Opportunities and threats to biodiversity from land-based production of biomass for bioenergy purposes

Based on literature and six country studies (Belgium, Denmark, Finland, Netherlands, Sweden, Slovakia) this paper discusses the compatibility of the EU 2020 targets for renewable energy with conservation of biodiversity.We conclude that increased demand for biomass for bioenergy purposes may lead to a continued conversion of valuable habitats into productive lands and to intensification, which both have negative effects on biodiversity. On the other hand, increased demand for biomass also provides opportunities for biodiversity, both within existing productive lands and in abandoned or degraded lands. Perennial crops may lead to increased diversity in crop patterns, lower input uses, and higher landscape structural diversity which may all have positive effects on biodiversity.In production forest opportunities exist to harvest primary wood residues. Removal of these forest residues under strict sustainability conditions may become economically attractive with increased biomass demand.An additional biomass potential is represented by recreation areas, road-side verges, semi-natural and natural areas and lands which have no other use because they have been abandoned, polluted or degraded.Whether effects of cropping of biomass and/or removal of biomass has positive or negative impact on biodiversity depends strongly on specific regional circumstances, the type of land and land use shifts involved and the associated management practices in general. However, it is clear that in the six countries studied certain types of biomass crops are likely to be more sustainable than others.     

Techno-economic analysis of H2 production processes using fluidized bed heat exchangers with steam reforming – Part 1: Oxygen carrier aided combustion

This work presents the techno-economic assessment for a new process where a fluidized bed heat exchanger (FBHE) is used as heat source for steam reforming in a hydrogen production plant. This suggested process configuration is compared with a reference case representing a conventional steam methane reforming (SMR) large-scale hydrogen production plant. The use of a FBHE as a heat source for the endothermic reforming is an advantage because of the high heat transfer coefficient to the reformer tubes. The suggested process configuration utilizes oxygen carrier particles as bed material and a bubbling fluidized bed reactor with immersed reformer tubes to ensure sufficient heat production for the reforming and improved heat transfer to the reformer tubes compared a conventional plant. The results include a comparison of hydrogen production efficiency and levelized production costs (LCOH) of the two plants where the production efficiency is more than 11% higher and the LCOH is more than 7% lower for the suggested process configuration.     

On the intraday dynamics of oil price and exchange rate: What can we learn from China and India?

The main aim of this paper is to investigate the volatility determinants of crude oil and foreign exchange markets and jump spillover between them. We consider currencies of two major oil-importing countries (India and China) over the sample period of January 1, 2013 to October 31, 2019. We find evidence of positive return spillover from the oil to the foreign exchange market; however, there is a lack of return spillover in the other direction. Oil jumps appear to have a negative impact on exchange rate conditional volatility, and the latter responds asymmetrically to disentangled (positive and negative) oil price jumps. We also report disentangled exchange rate jumps' significant impact on conditional oil price volatility. These results, however, are asymmetric based on the nature of jumps and alternative oil price series. Finally, we do not find evidence of co-jump between the oil and foreign exchange markets. These results have important implications for investors and policymakers.