Process Loss Is More (Recycling)

Simon-Anthony-webEver heard the term “process loss”? And do you know what it means? Simon Anthony, waste partnership officer at Bristol City Council, explains exactly what it is, where and how it occurs and leaves it in Defra’s court to decide if it should even be counted in our recycling…

What is “process loss”? In waste terms it is the difference between the amount of waste entering a facility and the amount of product leaving the facility. This phenomenon is mainly present within operations which comprise composting practices, such as in-vessel composting (IVC), open windrow composting and mechanical and biological treatment (MBT) facility; it can be more accurately be referred to as “composting loss”. The “loss” is actually mostly water vapour, which is released to the atmosphere or typically collected through on-site irrigation systems and sent to waste water treatment facilities.

Process loss generates an accounting disparity between typical composting facilities and MBT facilities. This anomaly is apparent every time relevant local authorities’ submit statistics within Waste Data Flow (WDF). It should be noted that this analysis relates to the situation for English local authorities; the position for Welsh and Scottish local authorities is different.

An English local authority submitting data for using an IVC or open windrow composting facility can rightly assume 100 percent of contamination free green waste is recycled. However for every 100 tonnes that enters an IVC or open windrow composting facility, approximately 70 tonnes will leave the facility. The difference is process loss.

When a local authority submits data for WDF for an MBT facility only “outputs” can be counted as recycling. Therefore, for illustrative purposes only, every 100 tonnes that enter an MBT’s composting hall a local authority can only count what leaves the composting hall as recycling, circa 70 tonnes.

Figure 1: Waste Data Flow assumptions of waste through an IVC or open windrow facility
Figure 2: Waste Data Flow assumptions of waste through an MBT facility
  • 100 tonnes Green Waste into open windrow = 100 tonnes composted/recycled under WDF (70 tonnes compost and 30 tonnes process loss)
  • 100 tonnes “biofines” into MBT composting hall = 70 tonnes composted/recycled under WDF (70 tonnes compost only) – biofines are the largely biodegradable fraction of residual waste treated in an MBT’s composting hall.

Who Does It Matter?

So why does correct accounting of process loss matter? For LA’s that use MBTs, it matters greatly. The current system discriminates against MBT facilities resulting in a significantly depressed recycling rate. Despite the same composting process being used in both typical composting facilities and MBTs, and the product from both being used for Environment Agency approved beneficial land improvement purposes, LA’s are restricted from reporting the full recycling amount.

The West of England Waste Partnership (WoEWP) has been using New Earth Solutions’ (NES) MBT facility in Avonmouth, Bristol, since April 2011. The partnership contributes 120,800 tonnes per annum (tpa) of black bag residual waste to the facility, of which a portion is composted. Of the “biofines” waste which enters the MBT composting hall, on average 11 percent is lost as moisture to the local environment or tankered away for treatment. New Earth record the moisture content of waste in their composting hall which can be used as evidence of process loss. In real terms, of the 120,800 tpa (WoEWP) deliver into NES’ facility, 13,665 tonnes is process loss (based on 13/14 data). In other terms, 11 percent of what could be classed as recycling is not. The WoEWP predict that overall recycling rates would increase by around four percent if process loss could be accounted correctly.

The difficulty in accounting for process loss is the measure by which we use to prove it.

  • A general [incoming waste – outgoing waste] method could be used. This method gives an idea of process loss, although can be distorted if an MBT facility de-stocks a lot of product (not just compost-like output) during a month. This will, however, even out during an annualised cycle.
  • MBT facilities could use actual moisture loss data from windrow monitoring. This would show exact process loss although would require all MBT facilities using the same robust replicable method regardless of site or operator.
  • Finally, it could be assumed that any biofines entering the composting hall are classed as recycled (as with typical composting facilities). A method of weighing biofines into the composting hall would be required.

Whether process loss is counted, and the method by which it is accounted for, is a decision for Defra to make. It is important that a clear decision is made following consultation with industry representatives to provide local authorities with transparency of what can and cannot be classed as “recycling”. It is hoped that counting process loss will close the loop-hole that is evident in waste management, but which has no negative impact on anyone in the waste management industry; it makes MBT facilities more attractive and it gives LA’s that use MBT facilities the same recycling opportunity as other composting facilities.


Simon Anthony is a Chartered Waste Manager with over 10 years in the waste industry.  Simon’s experience comprises local authority waste partnerships, environmental consultancy and kerbside recycling project officer roles. Simon works as West of England Waste Partnership Officer managing disposal options for general waste from partner authorities.


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