Composting and Anaerobic Digestion (AD)

EPA Waste Data Release, July 2020

Reference year 2018

The quantity of Irish waste accepted for treatment at composting and anaerobic digestion facilities increased from 380,000 tonnes in 2017 to 436,000 tonnes in 2018. This is an increase of 15 per cent.

The figures do not include (i) home composting estimates, (ii) facilities which only treated their own waste, (iii) waste imported to Ireland for treatment and (iv) organic fines, arising from the pre-treatment of residual waste, accepted for biostabilisation which are reported separately (see below).

Figure 1 illustrates that the quantity of municipal biowaste accepted for composting and anaerobic digestion in 2018 was similar to that in 2017 (246,000 tonnes and 245,000 tonnes). It is evident from Figure 1 that the Food Waste Regulations (commercial and household) and the associated brown bin roll out have led to increases of the quantity of municipal biowaste accepted for composting/anaerobic digestion. However, the latest EPA household data show that only 43 per cent of Irish households have access to a brown bin. As a result, the majority of Ireland’s municipal biowaste, including food waste, is not yet separately collected and recycled. New EU waste legislation (the revised Waste Framework Directive (EU) 2018/851) means that the seperate collection of biowaste will be mandatory from end-2023. This should lead to a further increase in the quantity of municipal biowaste collected and recycled in Ireland in the years ahead.

Key Trends

• Municipal biowaste is largely made up of kitchen and canteen food waste, garden and park green waste, edible oils and fats. This type of waste represented the largest fraction (56 per cent) of all waste accepted for composting/anaerobic digestion in 2018 (Figure 2).
• The other main types of waste accepted for composting/anaerobic digestion in 2018 included wastes from agriculture, horticulture, aquaculture, forestry, hunting and fishing and food processing (26 per cent) and waste from waste management facilities and water/waste water treatment plans (14 per cent) (Figure 2). Table 1 lists all types of waste accepted at composting/anaerobic digestion facilities in 2018.
• Seventy per cent of biodegradable kitchen and canteen waste accepted for composting/ anaerobic digestion originated from households. The latest EPA Waste Characterisation Study found that one-third of residual (black bin) waste from non-household sources (restuarants, hotels, offices etc.) is suitable for composting/anaerobic digestion. To boost our recycling rates and reduce methane emissions from landfills, this waste should be diverted to brown bins and composted.
• Sixty-one per cent of the waste accepted for composting/anaerobic digestion in 2018 was composted rather than digested.
• Of the total quantity of waste accepted for composting/anaerobic digestion in 2018, 83 per cent was processed at facilities in Ireland while 17 per cent was transferred to facilities in Northern Ireland for composting/anaerobic digestion.
• Products of composting and anaerobic digestion were used in horticulture, landscaping and agricultural land treatment.

Biostabilised organic fines

In 2018, five composting facilities in Ireland accepted organic fines for biostabilisation. Organic fines arise from the mechanical treatment of residual waste. There has been a notable rise in the treatment of organic fines at composting plants in Ireland, up from around 50,000 tonnes in 2013 to 138,000 tonnes in 2018. This increase reflects the fact that most residual waste in Ireland is now pre-treated mechanically at waste facilities, for example by trommelling, before it is sent for recovery or disposal. The organic fines arising from this pre-treatment process undergo composting to reduce their biological activity to an EPA-approved standard. The biostabilised fines can then be used as landfill cover or an alternative agreed use without giving rise to odour and greenhouse gas emissions.