Issue 03/2016

Basics
the lack of well-identified environmental requirements, and
inexistence of well-established testing methods. However,
since year 2000 there are standard methodologies to
evaluate the suitability of a material for its organic recovery
by composting. EN 13432 [5] is one of the most recognized
standard norms that defines the procedure and the criteria to
determine the compostability of a material. Logos (fig. 2) and
certificates issued by several certification bodies such as DIN
CERTCO and VINÇOTTE in Europe, BPI in USA, and JBPA in
Japan, allow demonstrating the conformity of final products,
materials, intermediates, and additives with the specified
criteria in the standard compostability norms. Moreover, false
and misleading environmental claims are being pursue by
diverse organizations, such as Federal Trade Commission in
the USA, which imposed recently a USD 450,000 civil penalty
[6].
In order to obtain the different compostability logos
the testing must be conducted in laboratories which are
recognized by the certification bodies [7, 8].
Compostability testing
The different tests to be performed in order to determine
if a material, intermediate, additive or product can be
recovered through composting according to EN 13432 [5] (and
if applicable, in connection with ASTM D 6400 [9], ISO 18606
[10], ISO 17088 [11], EN 14995 [12]) are compiled in table 1 and
described in the next subsections.
Material characterization:
Each product shall be identified and characterized including
at least:
1. Information and identification of the constituents,
2. presence of regulated metals (Zn, Cu, Ni, Cd, Pb, Hg, Cr,
Mo, Se, As, Co [13]) and other hazardous substances to the
environment (F), and
3. content in total dry and volatile solids.
Biodegradation
Biodegradability is determined by measuring the carbon
dioxide produced by the sample under controlled composting
conditions following ISO 14855-1:2012 [16]. For this the
sample is mixed with compost and placed in bioreactors at
58 °C under continuous flow of humidified air. At the exit the
CO 2
concentration is measured and related to the theoretical
amount that could be produced regarding the carbon content
of the sample.
The biodegradability should be determined for the whole
material and individually for the constituents present at levels
between 1 and 10 % [17].
The minimum duration of the test is 45 days, in which a
positive control (cellulose) has to be biodegraded at least in
a 70 %, and the maximum duration set out in the standard
is 6 months, in which the sample has to be biodegraded in a
90 % to be considered as biodegradable in compost [18].
Figure 3 shows the different phases observed during
biodegradation tests. Phase A corresponds to the lag time
sometimes observed for initiate the biodegradation; Phase
B corresponds to the active biodegradation of molecules
into CO 2
and H 2
O; Phase C is the plateau zone reached
after biodegradation has taken place, and D determines
the ultimate level of biodegradation. After the first 45 days,
continuation of the biodegradation test could be necessary or
not depending on the biodegradation rate of the material and
the phase achieved.
Figure 3. Typical biodegradation curve.
Biodegradation, %
100
90
80
70
60
50
40
30
20
10
0
0
A
A Lag phase
B Degradation phase
C Stationary phase
D Degree of biodegradation
B
4 8 12 16 20 24 28 32 36 40 44
Time, days
C
D
Table 1. Summary description of tests to be performed under EN 13432:2000.
Test Standard Test duration Sample weight
Chemical characterization of material:
- Dry and volatile solids
- Regulated metals (Zn, Cu, Ni, Cd, Pb, Hg, Cr, Mo,
Se, As, Co [13])
- Hazardous substances (F)
- Infrared transmission spectrum
Biodegradation under industrial
composting conditions
Disintegration under ind. composting
conditions and physico-chemical Pilot-scale
properties of compost (total dry
solids, volatile solids, pH, N-NH 4
,
N-NO 2
, N-NO 3
, N, P, K, Mg, salt
content, density, and maturity level)
Ecotoxicity in 2 plant species:
- Garden cress (Lepidium sativum)
- Summer barley (Hordeum vulgare)
EN 13432:2000
PT-04-63
EN 13432:2000
ISO 14855-1:2012
EN 13432:2000
ISO 16929:2013
2 weeks 20 g in powder
6 weeks – 6 months 100 g in powder
12 weeks 2 kg in final form, 14 kg in powder
Lab-scale ISO 20200:2004 [15] 90 days (+ 90 days) 500 g in final form
EN 13432:2000
OECD 208 (2006)
3 weeks,
after disintegration test
(compost samples from pilot-scale
disintegration)
bioplastics MAGAZINE [03/16] Vol. 11 43