The natural approach to carbon capture and storage

Materials World magazine
,
1 Dec 2017

Architect Peter Wilson* takes a closer look at the natural approach to carbon capture and storage in the UK.

Heating in homes and businesses accounts for 32% of the UK’s total carbon emissions – a reflection of the country’s long-term reliance on fossil fuels and its historically poor construction and insulation standards. Slowly, we are being weaned off the former – in 2016, 47% of the nation’s electricity came from low-carbon sources, around double the 2010 level. The average household energy consumption has also decreased by 17% since 1990.

These achievements are highlighted in the government’s recently published Clean Growth Strategy, as is the statement that the country played a central role in securing the 2015 Paris Agreement on climate change. This agreement was with 195 countries, representing over 95% of global economic activity, signing up to stretch their individual national targets to keep global temperature increase below 2ºC. However, in his Autumn Statement on 25 November 2015, only days ahead of the Paris meeting, the then Chancellor George Osborne cancelled the £1bln competition the UK Government had initiated to commercialise Carbon Capture and Storage (CCS) in the UK. 

Tackling climate change 

This capital finance, plus additional operational funding, was intended to support the design, construction and operation of the UK’s first commercial-scale CCS projects, with a range of other outputs, such as generating learning and driving down the cost of CCS (technology only tested at relatively small scale). In addition, it planned to test and build familiarity with a CCS-specific regulatory framework, encourage industry to develop suitable CCS business models, and contribute to the development of early infrastructure for carbon dioxide transportation and storage. All laudable ambitions, and ones that would have placed the UK ahead of others in the research and development of a technology, estimated by the International Energy Agency, to have a global market value of over £100bln, and potentially worth between £5bln-£9bln a year to the UK by 2031.

Why the reliance on CCS as part of the UK’s drive to meet its emission targets? Indeed, what exactly is CCS? At it’s simplest, it is a family of technologies designed to tackle global climate warming by capturing carbon dioxide at power stations, industrial sites or even directly from the air and permanently storing it underground. There are at least three different types of CCS systems suitable for application to fossil fuel power stations – post-combustion, pre-combustion and oxyfuel.

The fundamental process involved in the full-scale value chain application of each can be most easily understood as CO₂ captured at industrial plants being liquefied and stored temporarily on site before being transported by ship to a coastal storage site equipped with pipelines, where it is again temporarily housed. 

From there, the CO₂ is piped via undersea pipelines far out into the ocean, where it is injected into a permanent reservoir (either suitable geological formations, deep underground saline aquifers or disused oil fields) located around one mile below the seabed. In the case of oil fields, the process is known as enhanced oil recovery, in which the CO₂ forces out any remaining pockets of oil that would otherwise prove difficult to extract. 

The Clean Growth Strategy has resurrected the possibility of support to develop technology, albeit with a considerably smaller financial commitment – the £99m
now mooted having to be shared with technology and research in agri-tech, land use and waste and resource efficiency.

Given that the two developer consortia shortlisted for the previous £1bln of funding had each expended multi-million pound sums undertaking front end engineering and design (FEED) studies to de-risk aspects of their proposals, the government’s proposition that this smaller investment can be used to drive down the cost may prove to be a tad optimistic, especially as experts agree on one thing – it won’t be cheap. 

Conflicting statements  

At almost the same time as the UK Government was announcing its latest plans, two other countries expected to develop complementary processes released conflicting statements. The Netherlands’ coalition government agreed to set more ambitious climate goals than the EU, with the aim of a 49% reduction in CO₂ emissions by 2030 and to deliver, through the use of CCS, at least 20 million tonnes of the total 56 million CO₂ emission reductions its targets require.

To make this happen, a €4bln programme to support investment in CCS and other low-carbon technologies has been put in place. Part of these plans were for work to be carried out in collaboration with the UK and Norway, but the latter has, almost simultaneously with the Netherlands’ announcement, stepped away from its previous commitment to CCS by slashing expected state investment by over 90%, in response to growing political doubts about the cost. 

The investment required is the continuing barrier, but there are also questions as to whether CCS is the most economically viable or environmentally responsible route to meeting the climate challenge. Recent figures suggest that to push the development of the technology, the oil and gas industries are seeking subsidies averaging €96 per tonne of CO₂ stored, a relatively meaningless figure to most of us until compared with other approaches to carbon sequestration. The most obvious of these is forestry where, through photosynthesis, the power of the sun is used to consume CO₂. This mechanism splits the molecule into its component parts, with the carbon atoms then released, creating complex sugars that go on to become cellulose, the building block of wood. The necessary waste product is the oxygen that we breathe – hence the reason why unmanaged rainforest depletion should be avoided.  

The UK’s Clean Growth Strategy recognises the value of trees in its ambition to establish a new network of forests in England (including new woodland on farmland) and to fund larger scale woodland and forest creation. The UK Government has an aim to plant 11 million trees and increase the amount of UK-grown timber used in construction. Were these trees all to be planted immediately, it is likely they would have around 15 years of growth before any CCS facility had come on stream, during which time every cubic metre of timber would have absorbed the equivalent of 742kg of atmospheric CO₂ – at a quarter of the cost of the anticipated annual subsidy for CCS. And this is a built-in cost, as trees effectively capture and store carbon for free.

The built environment

This brings us back to the built environment, particularly UK industry and homes, which together, through heating and other power consumption requirements, generate 32% of our total national emissions. 

While the Clean Growth Strategy sets out plans for reducing energy consumption and improving construction quality, architects and others in the industry have long been aware of the need for environmentally responsible methods of building and for the selection of renewable, sustainable materials. Indeed, the 21st Century has witnessed something of a transformation in the use of timber in construction, as well as recognising the value of this built resource with low, zero, or negative (negawatts) consumption and emissions. 

The development of advanced solid timber products has taken this to new levels, with increasing numbers of large-scale urban blocks being constructed from wood. In London, at Dalston Lane, a large solid timber construction has been completed. Comprised of 121 apartments on 12,500 sq/m of floor space and with a further 3,500 sq/m of commercial space, 4,650 cu/m of solid, cross laminated timber panels form the walls, floors and roofs of the 10 storey complex and lock up some 3,450 tonnes of atmospheric CO₂.

At the other extreme, a three-bedroom timber-framed house will use around 6 cu/m of timber and lock up almost 4.5 tonnes of atmospheric CO₂ which, with Government ambitions to construct 250,000 houses per annum using predominantly prefabricated systems, would amount to approximately 1.125 million tonnes being stored in timber-based dwellings each and every year. 

Previous multi-billion pound plans for CCS schemes at Drax and Peterhead, UK, power stations were slated to capture and store 2 million and 1 million tonnes of CO₂, respectively. This raises questions about national strategic investment priorities. While debate continues, the importance of trees should not be lost – their inherent value is more than simply one of economics.

*Peter Wilson is director of Edinburgh-based Timber Design Initiatives Ltd. He has recently published a book, The Modern Timber House in the UK.