UK study finds Bio-SNG could offer 90% reduction in lifecycle CO2; lower cost of carbon abatement than electrical solutions for transport applications
|Cost of carbon abated for transport applications. Click to enlarge.
Bio-SNG (Synthetic Natural Gas) delivered via the gas grid offers CO2 lifecycle savings of up to 90% compared with fossil fuel alternatives, and offer sa more cost-effective solution than electricity for carbon abatement in transport applications, according to a new feasibility study published by National Grid (UK), the North East Process Industry Cluster (NEPIC) and Centrica. The report was prepared by Progressive Energy and CNG Services.
Unlike biomethane produced by anaerobic digestion, Bio-SNG is formed by the conversion of thermally-derived syngas—i.e., via the gasification of biomass waste—into methane. Feedstocks can include more durable material such as woody biomass and wastes that are not broken down in traditional anaerobic digester plants. Although anaerobic digestion of organic material has been widely accepted as an important renewable energy technology, the production of Bio-SNG will required to move to higher levels of fossil fuel replacement, according to the report.
Bio-methane retains all the attributes of natural gas, with the crucial advantage that the fuel is renewable, offering substantial Carbon Dioxide savings. Few other renewable vectors are as fungible, with so few demand-side constraints. Biomethane can, and is being produced via the upgrading of biogas from Anaerobic Digestion. However, in order to achieve a step change in production capacity, alternative approaches such as via thermal routes (termed “Bio-SNG”) are necessary. Whilst technically feasible, this approach is less mature than anaerobic digestion.—“Bio-SNG Feasibility Study”
The feasibility study appraises the opportunity afforded by Bio-SNG, building on a review of the issues associated with biomass sourcing, a detailed analysis of the technology options and applicability for injection into the UK grid, as well as a financial appraisal. It draws on benchmarking data to demonstrate the full lifecycle carbon dioxide savings and also demonstrates that the Bio-SNG route is a very cost effective route for decarbonization compared with other renewables. The report also suggests proposals for implementation pathways, specifically how a Bio-SNG demonstration could be established in the UK’s North East.
Among the conclusions of the report are:
Regulatory. Implementation of Bio-SNG will only take place with the appropriate tax, incentive and legislative environment. In addition to the incentives structures, the regulatory environment must be clear and appropriate, particularly with regard to: requirements for gas injection, emissions directives, and how the use of waste as a feedstock is treated.
Feedstocks. It is likely that the development of Bio-SNG facilities will require the developer to go upstream into the supply chain for both grown and waste derived fuels, however, specification and quality control are vital determinants of project success.
Process and technology. The process technology review established that, in principle, the major process operations required to produce Bio-SNG can be identified and assembled from existing technology suppliers. The essential first condition that must be satisfied, according to the report, is that feedstock specification and the process design are matched; the gasifier in particular can not be omnivorous.
The report opts for the choice of an oxygen-blown direct bubbling fluidized bed gasifier, either pressurized or un-pressurized. Downstream of the gasifier the gas processing operations are conventional technology: heat recovery and power generation, gas scrubbing, water gas shift, methanation, conditioning and compression.
The report does not identify an optimized process configuration for energy consumption. There is a balance to be struck, it notes, between gasifier operating pressure, gas train pressures and compression loads and the power consumption for Bio-SNG export.
Carbon savings. A full lifecycle analysis of Bio-SNG production undertaken by North Energy Associates found that for many types of feedstock, the lifecycle CO2e savings of Bio-SNG compared with fossil fuel alternatives are typically ~90%. This saving is similar for both conventional heating and transport applications.
Cost of carbon abated. Strategically the UK needs to consider the most cost effective approach for decarbonizing, the report notes. For heating applications using natural gas as a counterfactual, Bio-SNG offers a cost per tonne of CO2e abated of ~£175/te. This compares very favorably with direct biomass combustion for domestic applications (£395/te) and for small commercial applications (£285/te), as well as with Ground source heat pumps (£5500/te).
For transport applications, Bio-SNG is significantly more cost effective than electrical solutions (either using grid electricity - £1,000/ te CO2e, or presuming offshore wind derived renewable electricity - £600/ te CO2e). However, the analysis does suggest that while Bio-SNG does offer significant carbon savings for the transport sector, on a cost per tonne abated of £400/ te CO2e, the heating sector is a preferable end market, the report suggests.
Along with all unconventional energy infrastructure development there is a need for novel financing strategies, as well as the necessary support regime. In terms of taking forward a UK demonstration project, the study indicates that Teesside is a highly attractive location because of its chemical industry, ability to utilise waste heat and co-products and extensive high pressure gas grid.