Composting Tea ( Leaves)

In recent months there has been much criticism of the use of plastic in teabags (see below) and the advice given is that where possible use loose tea, just in case the publicity has led to some deciding it is not worth the bother of composting tea it is worth reemphasising just how good used tea can be as a nutrient for the garden. Lawrence Hills in Grow Your Own Fruit and Vegetables, first published in 1971 by Faber and Faber, made the case for adding tea to the compost heap and nothing has changed apart from the fact that if tea bags are composted they should be plastic free, be torn open and emptied or the remains of plastic bags rescued after composting.

As with other kitchen waste it is best to collect the cooled tea leaves (or bags) after each pot or mug of tea, in a kitchen caddy along with other vegetable waste and only make the trip to the compost bin or worry when the caddy is full.

The leaves contain about half as much nitrogen as dried blood and more than poultry manure. Tea leaves contain approximately 4.4% nitrogen, along with, 0.24% phosphorus and 0.25% potassium the addition of tea to the compost heap will provide nutrients encouraging the decomposition process. All teas are not the same each variety of tea, black, green or red, will contain a different ratio of compounds but whichever you prefer they will make a useful addition to the compost bin particularly if collected in larger quantities from a local tea shop or café.

Tea leaves, and tea bags, can be added direct to the soil tea as mulch on the soil surface round the plants or to dig the leaves into the soil when preparing the plot. However, as a composter I would recommend composting rather than direct application as it saves time to treat the tea as any other compostable kitchen waste. One of the disadvantages in direct application is that the Tannic acid is in the tea can in some soils lower the pH, so it would be advisable to check the soil pH before the addition of tea leaves.

Photo

By Selena N. B. H. from Fayetteville, USA (English Westminster
Uploaded by JohnnyMrNinja) [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0
)], via Wikimedia Commons" 

Tea and Plastics in teabags

The plastic tea bag after composting

The loose tea brewed in a teapot or tea ball can be easily composted. Tea leaves are a good source of Nitrogen (Greens) organic material for the compost bin which will be moistened during the brewing process encouraging decomposition. The tea ball or strainer can be emptied directly into the kitchen caddy while loose leaves can be scooped from the pot into the caddy by hand, once cool.

Teabags are usually listed as compostable items but in recent years more and more composters have complained that the bags do not actually decompose when composted. In 2010 a report by Which? Gardening, found that six out of the seven largest tea bag manufacturers did not make fully compostable bags. This is because at the bags include a non-biodegradable plastic (polypropylene) so that they can be more easily heat-sealed during manufacture.  The bags may be described as “70% or 80%” compostable which includes the tea leaves and paper element of the bag but not the plastic.

Although each individual teabag is small they account for about 150 tonnes of polypropylene going to landfill, AD or composting a year in the UK alone. This is equivalent to about 165 million teabags a day. Many of these are composted in food waste.

The COOP announced in January 2018 that it was in the final stages of developing a plastic free biodegradable teabag for its own brand Fairtrade 99 teabags. The Coop which sells 367 million teabags a year hopes to have the new bags in their shops later this year.

PLASTIC-FREE TEA BAGS

Some teabags are already plastic free making the bags ideal for composting. This is list was published in April 2018:

  • Teapigs
  • Pukka Tea
  • Jacksons of Piccadilly
  • Twinings Pyramid tea bags
  • PG Tips pyramid teabags
  • Tetley’s catering range
  • Clipper string and tag teabags

 

Mike Armitage a gardener from Wrexham started a petition to get manufacturers to remove all plastic from tea bags after finding residue from teabags in his garden compost. Details of the 38 Degrees petition can be found at (https://you.38degrees.org.uk/petitions). The petition succeeded in persuading the UK's largest tea bag manufacturer Unilever/PG Tips to announce that they will remove plastics from their teabags. 

But the other leading UK teabag manufacturers are still using plastics in their teabags, although the following are expected to become plastic-free during 2018

  • Clipper pillow teabags (the string and tag Clipper teabags are already plastic free)
  • PG Tips standard teabags
  • Tetley teabags (Tetley string & tag teabags which are used mostly in their catering range of individually wrapped tea bags are plastic free).   
  • Co-Op 99 teabags

Compostable teabags made of a corn starch (SOILON) are sold by the Brew Tea Company and Teapigs. These will hot compost in about 6-8 weeks around 12 months in a cold composting system. The corn starch might be from GM plants  so there will be a need to compare the risks to the environment from the GM seeds from which the corn was grown with that from microplastics which is killing  ocean life now as well as cropping up in soil and fresh water.

Pukka Tea teabags are sewn by machine with cotton thread, not heat sealed, and do not contain plastic. The teabag paper is made of a blend of natural abaca (a type of banana) and plant cellulose fibres.

Fruit, herbal and green tea ranges may already use a compostable tea bag material which can be put straight in the compost bin.

 Composting Tea bags

Before the current concerns about plastic in teabags the advice when home composting was to use loose leaf tea or if using teabags that did not decomposing during the composting process i.e.  non-compostable bags:

  • tear open the bags before putting them in the bin
  • or sieve or pick them out after composting.

I have seen advice recently suggesting that to avoid the risk of the plastic entering the home compost bin, and eventually the soil, the bag should be emptied by cutting the top off the bag and tipping the tea residue into the kitchen caddy allowing it to be treated as loose tea. Unfortunately, if the empty bag is put into the household (landfill) rubbish bin the plastic will still enter the soil.

 

Sources:  http://moralfibres.co.uk/is-there-plastic-in-your-tea/

 

 

Teabag decomposition in a Wiggo pod wormery.

Magnified tea bag fibres after composting

We have been running a series of experiments comparing the decomposition rates of various plant material in a Wiggo Pod wormery. The primary purpose is to provide photos for free use by composters giving talks, schools, etc.

This set of photographs shows the decomposition of a PG tips tea bag (which contains plastic to assist in heat sealing of the bag, and fruit tea teabags

  • The original teabag tabletop display

  • Tea bags from PG tips and a herbal tea in a Wiggo pod

  • Tea bags being composted in a Wiggo pod with paper

  • Remains of teabag from Wiggo pod

  • Remains of teabag from Wiggo pod

  • Magnified teabag plastic mesh

Composting and Microplastic particles in soil

In the past the main concerns when composting teabags were based on the fact that the uncomposted teabags looked unsightly spread on the garden but now the main problem relates to the presence of microplastic resulting from degradation of plastic in the teabags. Joining  other plastic-coated items in the soil and in drainage water.

A recent study* has shown that earthworms can be play a significant role in transporting microplastics in soils by means of their casts, burrows, etc with the smaller particles being carried to a deeper depth. This may increase the risk of the microplastic entering groundwater. As treating the soil with compost as a mulch  tends to attract worms the risk to groundwater  should be borne in mind when diposing of  teabags and the subsequent treatment after use.

 Using compost as a mulch is good for plant health and in attracting worms to the treated area but other research** has shown that polyethylene microplastics in plant litter deposited on the soil surface resulted in reduced worm growth and higher mortality. Would the same results be seen if a mulch of compost contaminated with plastic microparticles from a significant quantity of “plastic” teabags was used in the compost. 

But it is not just teabags there are other plastic-coated items that might find their way into the compost bin, or council waste stream, that can produce microparticles. Check the label, do not confuse home compostable products with those compostable at an industrial site.  Compostable products such as those containing PLA (poly-lactic acid) do not contain petroleum-based plastics and will decompose to form healthy compost.

We can all play a small part in protecting our environment.

 

References and background source:

*Microplastic transport in soil by earthworms” by Matthias C. RilligLisa Ziersch & Stefan Hempel Scientific Reports volume 7, Article number 1362(2017)  

 ** Earthworms on a microplastics diet Julia Fahrenkamp-Uppenbrink Environ. Sci. Technol.10.1021/acs.est.5b05478 (2016).  http://science.sciencemag.org/content/351/6277/1039.1/tab-article-info

Plus

The Environmental Hazards Inherent in the Composting of Plastic-Coated Paper Products WILL BRINTON1 , CYNDRA DIETZ2 , ALYCIA BOUYOUNAN2 , DAN MATSCH2  http://www.ecocycle.org/files/pdfs/microplastics_in_compost_white_paper.pdf

Microplastics in compost

A study by Nicolas Weithmann and colleagues from the University of Bayreuth, Germany investigated the potential of organic fertilizers from biowaste fermentation and composting as an entry path for microplastic particles into the environment. 

All samples from plants converting biowaste to fertiliser. (composts, digestates, and percolate-leachates from digestion, which is used as liquid fertilizer) contained plastic particles, but amounts differed significantly with substrate pre-treatment, plant, and waste (for example, household versus commerce) 

Composters will be concerned to know that 20-24 pieces of microplastics per kg of dry weight were found in the compost from a composting plant processing biowaste from households with green clippings from the area.  While waste from the public using the green waste collection system  is much more likely to be contaminated than home composted material  it does indicate an are of potential concern.

However, the quantity of microplastic present was small when compared with compost produced from supermarket waste which contained 895 pieces >1 mm per kg dry weight.

 

Read more

Rachel Ehrenberg (April 5, 2018). “Microplastics may enter freshwater and soil via compost.” Science News

Reference

Weithmann, N., et al. (2018). “Organic fertilizer as a vehicle for the entry of microplastic into the environment.” Science Advances (published online April 4, 2018).