Modelling short-rotation coppice and tree planting for urban carbon management - a citywide analysis

© 2015 British Ecological Society The capacity of urban areas to deliver provisioning ecosystem services is commonly overlooked and underutilized. Urban populations have globally increased fivefold since 1950, and they disproportionately consume ecosystem services and contribute to carbon emissions, highlighting the need to increase urban sustainability and reduce environmental impacts of urban dwellers. Here, we investigated the potential for increasing carbon sequestration, and biomass fuel production, by planting trees and short-rotation coppice (SRC), respectively, in a mid-sized UK city as a contribution to meeting national commitments to reduce CO2 emissions. Iterative GIS models were developed using high-resolution spatial data. The models were applied to patches of public and privately owned urban greenspace suitable for planting trees and SRC, across the 73 km2 area of the city of Leicester. We modelled tree planting with a species mix based on the existing tree populations, and SRC with willow and poplar to calculate biomass production in new trees, and carbon sequestration into harvested biomass over 25 years. An area of 11 km2 comprising 15% of the city met criteria for tree planting and had the potential over 25 years to sequester 4200 tonnes of carbon above-ground. Of this area, 5·8 km2 also met criteria for SRC planting and over the same period this could yield 71 800 tonnes of carbon in harvested biomass. The harvested biomass could supply energy to over 1566 domestic homes or 30 municipal buildings, resulting in avoided carbon emissions of 29 236 tonnes of carbon over 25 years when compared to heating by natural gas. Together with the net carbon sequestration into trees, a total reduction of 33 419 tonnes of carbon in the atmosphere could be achieved in 25 years by combined SRC and tree planting across the city. Synthesis and applications. We demonstrate that urban greenspaces in a typical UK city are underutilized for provisioning ecosystem services by trees and especially SRC, which has high biomass production potential. For urban greenspace management, we recommend that planting SRC in urban areas can contribute to reducing food-fuel conflicts on agricultural land and produce renewable energy sources close to centres of population and demand

Boletín oficial de la provincia de León: Num. 15 (05/05/1922)

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2011-201

A finite-volume-based two-dimensional wall-flow diesel particulate filter regeneration model

Many existing diesel particulate filter (DPF) models do not sufficiently describe the actual physiochemical processes that occur during the regeneration process. This is due to the various assumptions made in the models. To overcome this shortcoming, a detailed twodimensional DPF regeneration model with a multistep chemical reaction scheme is presented. The model solves the variable density, multicomponent conservation equations by the pressure implicit with splitting of operators (PISO) scheme for inlet and outlet channels as well as the porous soot layer and filter wall. It includes a non-thermal equilibrium (NTE) model for the energy equation for porous media. In addition, for the first time, experiments on the DPF were conducted to determine the interstitial heat transfer coefficient inside the DPF porous wall. The results compare well with an in-house one-dimensional model and subsequently this was used in the new two-dimensional model. By using this detailed two-dimensional model, some interesting observations of the DPF regeneration process were revealed. These included flow reversals and asymmetry in the filter channels

Fuelling expectations: a policy-promise lock-in of UK biofuel policy

Controversy over EU-wide biofuel policy resonated within the UK, fuelling policy disagreements among UK public authorities. They disagreed over how to protect a space for future second-generation biofuels, which were expected to overcome harm from first-generation biofuels. The UK government defended rising targets for available biofuels as a necessary stimulus for industry to help fulfil the UK’s EU obligations and eventually develop second-generation biofuels. By contrast, Parliamentary Select Committees opposed biofuel targets on grounds that these would instead lock-in first-generation biofuels, thus delaying or pre-empting second-generation biofuels. Those disagreements can be explained by different institutional responsibilities and reputational stakes towards ‘promise-requirement cycles’, whereby techno-optimistic promises generate future requirements for the actors involved. The UK government’s stance illustrates a ‘policy-promise lock-in’, a dilemma whereby promised support is a requirement for credibility towards technology innovators and thus technoscientific development – but may delay the redirection of support from incumbent to preferable emerging technologies. Thus the sociology of expectations – previously applied to technological expectations from technology innovators – can be extended to analyse public authorities

Road User Charging – Pricing Structures.

This project considers the extent to which the public could cope with complex price or tariff structures such as those that might be considered in the context of a national congestion pricing scheme. The key elements of the brief were: • to review existing studies of road pricing schemes to assess what information and evidence already exists on the key issues; • to identify what can be learned about pricing structures from other transport modes and other industries and in particular what issues and conclusions might be transferable; • to improve the general understanding of the relationship between information and people’s ability to respond; and • to recommend what further research would be most valuable to fill evidence gaps and enable conclusions to be drawn about an effective structure

Bioenergy with carbon capture and storage (BECCS) potential in jet fuel production from forestry residues: A combined Techno-Economic and Life Cycle Assessment approach

In this study, the economic and environmental feasibility of a process configuration based on the Bioenergy and Carbon Capture and Storage (BECCS) concept is assessed. The research analyses the production of jet fuel from forestry residues-derived syngas via the Fischer-Tropsch (FT) technology. Further, the CO2 removed in the syngas cleaning section is not released to the environment, instead it is permanently sequestrated. The produced Sustainable Aviation Fuel (SAF) has the potential to achieve negative emissions. The present research is a one-of-a-kind study for the jet fuel production within the BECCS concept. The process has been modelled within the Aspen Plus and Matlab software to obtain detailed and realistic mass and energy balances. Based on these balances, the technical, economic and environmental parameters have been calculated. Based on a plant that treats 20 dry-t/h of forest residues, 1.91 t/h of jet fuel are produced, while 11.26 t/h of CO2 are permanently stored. The inclusion of the CCS chain in the biorefinery increase the minimum jet fuel selling price from 3.03 £/kg to 3.27 £/kg. The LCA results for global warming show a favourable reduction in the BECCS case, in which negative emissions of −121.83 gCO2eq/MJ of jet fuel are achieved, while without CCS case exhibits GHG emissions equal to 15.51 gCO2eq/MJ; in both cases, the multi-functionality is faced with an energy allocation approach. It is, then, evident the significant environmental advantages of the BECCS process configuration. Nevertheless, financial feasibility can only be attained through the implementation of existing policy schemes and the formulation of new strategies that would reward negative emissions. The application of the UK's policy “Renewable Transport Fuel Obligation” and a hypothetical scheme that rewards negative CO2 emissions, breaks-even the Minimum Jet fuel Selling Price (MJSP) at 1.49 £/kg for a certificate and carbon price of 0.20 £/certificate and 246.64 £/tonne of CO2

Understanding the intensity of UK policy commitments to nuclear power: the role of perceived imperatives to maintain military nuclear submarine capabilities

The UK Government has long been planning to build up to 16 GWe of new nuclear power – a proportional level of support unparalleled in other liberalised energy markets. Despite many challenging developments, these general nuclear attachments show no sign of easing. With many viable alternative strategies for efficient, secure, low-carbon energy services, it is difficult to explain these commitments solely in terms of officially-declared policy rationales. A variety of possible reasons are suggested for the persistent intensity of UK attachments to civil nuclear power. Each is taken here as a basis for systematic hypothesis testing. And one additional hypothesis is also interrogated that has hitherto been virtually entirely neglected – about maintaining national capabilities to build and operate nuclear propelled submarines. To explore and test this idea, this paper analyses linkages between UK military and civilian nuclear sectors in terms of high-level policy processes around supply chains, skills and expertise. Especially interesting is the critical juncture between 2003-2006, when stated policy moved radically from nuclear power as ‘unattractive’ to calls for a ‘nuclear renaissance’. In this period, especially intense activity can be observed around UK nuclear submarine capabilities. Among many factors, we conclude it is difficult fully to comprehend the persistent intensity of official UK attachments to nuclear power, without also considering aims to maintain nuclear submarine capabilities. Yet this aspect is entirely undocumented anywhere in UK energy policy literatures. To acknowledge this, is not to entertain a conspiracy theory. It can be understood instead, in terms of more distributed and relational dynamics of power. Building on literatures in political science, we refer to this as a ‘deep incumbency complex’. Such an evidently under-visible phenomenon would hold important mplications not only for UK nuclear strategies, but also the wider state of British democracy

Energy and greenhouse gas balance of the use of forest residues for bioenergy production in the UK

Life cycle analysis is used to assess the energy requirements and greenhouse gas (GHG) emissions associated with extracting UK forest harvesting residues for use as a biomass resource. Three forest harvesting residues were examined (whole tree thinnings, roundwood and brash bales), and each have their own energy and emission profile. The whole forest rotation was examined, including original site establishment, forest road construction, biomass harvesting during thinning and final clear-fell events, chipping and transportation. Generally, higher yielding sites give lower GHG emissions per 'oven dried tonne' (ODT) forest residues, but GHG emissions 'per hectare' are higher as more biomass is extracted. Greater quantities of biomass, however, ultimately mean greater displacement of conventional fuels and therefore greater potential for GHG emission mitigation. Although forest road construction and site establishment are " one off" events they are highly energy-intensive operations associated with high diesel fuel consumption, when placed in context with the full forest rotation, however, their relative contributions to the overall energy requirements and GHG emissions are small. The lower bulk density of wood chips means that transportation energy requirements and GHG emissions are higher compared with roundwood logs and brash bales, suggesting that chipping should occur near the end-user of application. © 2011 Elsevier Ltd