NG/E&Y potential: 1,042 - 8,328m m3
Credible potential: 0 - 100m m3
The greatest mystery about NG/E&Y’s figures for biodegradable waste is exactly what material they had in mind, and how they expected it to be used. The main biodegradable components of municipal and commercial wastes are food wastes. But these are considered separately.[1]
Other technically-biodegradable components of the waste stream include garden waste, paper, card and wood. None of these is very suitable for digestion. Wood waste is also considered separately, but for wont of an alternative explanation, the rest must be the core of what NG/E&Y had in mind for this category.
Garden waste was and continues to be composted primarily. There is an established infrastructure and market for this product. It is unsuitable for digestion, because of the amount of fibre/lignin/non-putrescibles. It could be suitable for gasification (see below) if suitably prepared, but it is doubtful that the challenge is worth the reward compared to the straightforward and commercial option of composting. Were it diverted from composting, then there would be a danger of the market resorting to less environmentally-friendly options such as peat.
Paper and card are also not suitable for digestion, at least without significant technological breakthroughs that were not in prospect in 2009 and have not materialised since. They are eminently suitable for thermal processes, and form (along with plastics) the bedrock of the UK’s significant expansion of Energy-from-Waste. They could be gasified instead of incinerated, if the technology were sufficiently mature and competitive (see below). Much of it can also be (and substantially is) recycled.
The recycling rate for paper and cardboard is widely reported to be around 80%.[2] Government statistics provide only partial information, and are structured in such a way that it is difficult to get a complete picture.[3] The real picture appears to be around 7.5m tonnes of paper recovered from around 10.8m tonnes of paper and cardboard consumed.[4]The unrecoverable proportion is thought to be around 22%, which leaves around 970,000 tonnes available for gasification, if it can be recovered and converted to a useful fuel economically, without diverting material from currently-preferred recovery options.
The recycling rate for paper and card was already high by 2009.[5] And total volumes were higher, as the cyclical and structural declines in paper consumption had only just begun. However, over half of the recovered material was exported, mainly to China. There were problems with demand from both native and foreign recyclers.[6] NG/E&Y might reasonably have assumed that most of the exported, some of the native-recovered and some of the unrecovered material could be available for gasification – perhaps as much as 5-6m tonnes. This would have turned out to be much too optimistic, but the availability of feedstock is anyway one of the lesser problems with this option to increase the volumes of green gas (see below).
[1] It is possible that their “food waste” referred only to commercial food waste, and their “biodegradable waste” is short for Biodegradable Municipal Waste, including municipal food waste. But they do not describe them as so, and their figures for food waste would be even less explicable if they excluded the municipal component. It would, however, help to explain the largely inexplicable figures for biodegradable waste, though not remotely enough to make 8,328m m3 a possibility.
[3] For example, the Let’s Recycle report relied, like many on DEFRA’s, UK Statistics on Waste, Mar 2019 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/784263/UK_Statistics_on_Waste_statistical_notice_March_2019_rev_FINAL.pdf. This reports that, of 4,749,000 tonnes of waste paper and cardboard produced in 2017, 3,754,000 was recycled/recovered. Paper and card would also have been a substantial proportion of the 700,000 tonnes that went to Energy-from-Waste. However, this appears to be the subset of paper that is used for packaging, within a report that is focused on household waste.
[4] 7.5m tonnes from https://paper.org.uk/the-paper-industry/key-statistics/. 10.8m tonnes is from the CPI’s most recent annual report, for 2017/18 (https://paper.org.uk/PDF/Public/Publications/Annual%20Reviews/CPI%20Annual%20Review%202018.pdf). The CPI do not seem to have published a more recent report. 22% unrecoverable is from the same source. The figures for total consumption appear to include an extra category (transit packaging) compared to the figures below for pre-2010. We can compare, for instance, the figures for 2010 consumption: 13m tonnes according to CPI’s 2017/18 annual report, but 10.7m tonnes according to their 2012/13 annual report. Without transit packaging, UK consumption of paper and board is probably around 9.5m tonnes.
[5] Government data is hard to find for the years before 2010. The archived spreadsheet at https://webarchive.nationalarchives.gov.uk/20100403161511/http://www.defra.gov.uk/evidence/statistics/environment/waste/wrpaper.htmindicates a recycling rate of 71% in 2007 (8.6m tonnes recovered vs 12.1m consumed), rising rapidly from 65% in 2006 and 50% in 2003. The Confederation of Paper Industry’s annual report for 2012/13 suggests the rate was closer to 80% by 2009, largely because consumption (10.3m tonnes) had fallen faster than recovered material (8.1m tonnes) because of the Crash and increasing use of electronic media. (https://paper.org.uk/PDF/Public/Publications/Annual%20Reviews/CPI%20Review%202012-13.pdf). Comparing recovery with consumption over-states the amount of residual paper available for other uses, as not all paper that was consumed would appear in the waste stream (e.g. if burnt on-premises). Around 20% of paper and card is thought to be unrecoverable.