INTRODUCTION: Most biocompostable plastics are only certified for industrial composting units. Since many products made with biocompostable plastics are intended for the domestic end-market, and are not currently recycled in the UK, this leaves any consumer following the certification to the letter with limited disposal options for their biocompostable plastic waste aside from black bag rubbish (landfill or incineration), negating much of the bioplastics’ ecologically-friendly appeal.
Does this mean, however, that biocomposable plastics are not compostable at home at all, or just within the 6 month upper limit required for certification? Would a 2-year time-frame be sufficient to break down commonly-found biocompostable plastic single-use items in a domestic compost heap?
The issue of plastic waste is a global one, and biocompostable plastics may be part of the solution, but at the moment there lacks the industrial composting or recycling infrastructure to handle the waste coming from biocompostable single-use items. This experiment seeks to determine if backyard composting is a suitable alternative to landfill, for limited amounts of biocompostable plastic waste.
HYPOTHESIS: Biocompostable plastics will show clear evidence of deterioration in a domestic compost heap, at least as much as other hard-to-compost organic material comparisons such as wood and fruit stones, but will not have completely biodegraded within a 2-year time frame. This is due to the temperature within the substrate not often reaching the 55-60 deg C of an industrial composting unit, and the domestic heap’s gentler microbial action and infrequent turning. Petrochemical plastics added as controls are not expected to shown any signs of deterioration.
MATERIALS: 26 subjects are to be put into the compost heap, as follows:
Biocompostable Plastics: a Vegware tub lid (clear #7 PLA); a compostable coffee cup; a Vegware coffee cup lid (opaque #7 PLA); a Vegware fork (white); some biocompostable film packaging (for If You Care kitchen cloths – marked OK Compost); some biofoam packing peanuts.
Organic Materials: a used loofah; a wooden fork; an avocado stone; some used soapnuts; a real cork; a compound (recycled) cork; some boiled wool fabric; some organic cotton calico fabric; two rubber (aka elastic) bands.
Petrochemical Plastics (as controls): a Solo® tub lid (clear #1 PETE); a Plastico 'Sunlite' spoon (clear #6 Polystyrene); a Pukka teabag envelope (paper lined with a thin plastic layer).
Teabags and Teabag Envelopes: From Java Republic, Solaris, Buddha Teas, Steenbergs and Les Jardins de Gaia. All these organic teabags and envelopes are either paper or biocompostable plastic and contain no petrochemical plastic seals or packaging. They form part of a related research project and shall be documented separately.
Other: An If You Care kitchen sponge cloth (cellulose cotton mix, marked OK Home Compost); a fabric citrus fruit net (material unknown); two types of felt fabric (green, material unknown).
EQUIPMENT: An existing home-composting green plastic container and lid; marine-grade stainless steel zip ties, stamped with identifying numbers or letters; thermometer.
METHOD: All materials are to be individually secured with stainless steel identity tags and put into a home compost bin, being covered with domestic compost waste as would occur in the normal course of home composting. The temperature of the heap is to be internally measured monthly, at midday and 6pm, to give an idea of upper temperatures reached. After one year, the materials are to be carefully extracted and examined, to determine the level of deterioration (if any). The compost will then be turned and the materials reintroduced, if required, for a further year. After the second year, the materials are to be extracted a final time and findings recorded.
DISCLAIMER: This is not a measured scientific experiment, it is an amateur study which will determine visually whether any composting action has occurred on the materials in question. The degree to which composting has progressed will be subjective. No testing is to be done for toxins or other substances invisible to the naked eye or to the overall quality of the resulting compost.
So, now, let’s get mulching! Compost heap internal temp on start day, 21/06/18 @ 12pm: 29 deg C; @ 6pm: 30 deg C...