Microsoft Word - Environmental benefits of recycling 2010 update.doc

Table 81 Carbon binding and storage function in the studies

Study

number

Carbon Binding

inclusion

Carbon Storage

inclusion

Amount

1  Yes No

Binding:  48  kg of CO2‐equivalent

per ton of biowaste composted

or

173  kg of CO2‐equivalent per ton

of compost

2  No Yes 15% of initial quantity

3  No No ‐ 

4  No No ‐ 

5  Yes No 40 ‐ 65  tons per acre

6  No Yes 48  kg of C per ton of compost

The fate of the carbon is also related to the degradation conditions assumed in the case of composting and
landfill. Different assumptions regarding this issue can lead to completely different results. For instance, in study
no 3, the degradation occurs in either assumed aerobic or anaerobic conditions and the results revealed that
home composting under assumed artificial total anaerobic conditions produces results 94 times higher for climate
change than the corresponding assumed total aerobic home composting.

Material substitution

The only treatment options that produce a recovered material are composting and anaerobic digestion. The
recovered material from both these activities can be used for substitution of many fertilising products, the most
common of which are fertiliser, peat, mulch and soil conditioner.

Out of the six studies that contain either of these two treatment methods, only one assumes no substitution of
virgin material at all (study no 5). However, the rest of the studies claim that there can be high benefits from the
avoidance of virgin production in some impact categories. For example, peat substitution leads to high savings in
climate change as peat is assumed to be of fossil origin and releases high concentrations of methane after being
applied. The substituted products for composting and anaerobic digestion, as well as the carbon binding issue are
presented in the Table 82.

Table 82 Substituted products for composting and anaerobic digestion and assumptions regarding carbon storage

Study

number

Substituted material by

compost

Substituted material by

digestate

Carbon storage

inclusion

(^1) Fertiliser / No
(^2) Peat and inorganic fertiliser / Yes
(^3) Cow manure / No
(^4) Fertiliser Fertiliser No
(^5) No substitution / Yes
(^6) 30% peat, 60% fertiliser 30% peat, 60% fertiliser Yes
(^7) / Fertiliser No
Nevertheless, the influence of the indirect avoided emissions on the overall results cannot be determined
precisely since the results are not consistent for each substituted material and the inventory data is not
published. An important observation from the table, however, refers to study no 5. Even if this study assumes no
material substitution, the result for composting in climate change is net negative, which means that the benefits
are greater than the burdens. This fact indicates that there are great benefits in carbon binding (the only other
source for indirect emissions) which might supersede the benefits stemming from material substitution.

Level of technology and relevant efficiencies

The assumptions regarding the technological status involved in the waste management system are vital for the
overall results but also for allowing a minimum common ground for comparison of results across studies. In