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Under the Lid – Meet Professor John Ward

Prof John Ward taking water and soil samples from an historic landfill site

John Ward is Professor of Synthetic Biology for Bioprocessing at UCL's Department of Biochemical Engineering. He is also a keen gardener and composter and enjoys isolating novel bacteria from all kinds of environments.

John is interested in looking at how we might use new kinds of bacteria to help break down plastic, which is crucial to our work at UCL's Plastic Waste Innovation Hub where a diverse team of UCL researchers and industry, government, and the public are investigating ways to solve the environmental challenge of plastic waste. One aspect of this research involves finding new types of bacteria that can digest plastic waste. John has been characterising novel bacteria isolated from different soils and composts for several years, and he will be isolating new bacteria from composting plastics that might eventually help to recycle plastic waste.

Bacteria from a wormery in a London school

This bacteria was grown from a sample of ‘vermicompost’ or ‘worm compost’ from a London school wormery. Its colour and size reveals the huge diversity of different bacteria present in the worm compost. The black pigment is probably melanin made by a bacterial colony that secretes an enzyme call tyrosinase. Soil and compost bacteria are often pigmented and the agar plate shows many different pigmented bacterial colonies.

Bacteria from a flower pot at UCL

This bacteria was grown from soil found in a flower pot at UCL. The agar plate shows a background pigmentation of a blue compound called actinorhodin that is secreted from several of the small white bacterial colonies. There is less diversity of bacteria in this micro-environment compared to the rich diversity in the worm compost.

Bacteria isolated from an enrichment composting experiment using PET plastic

This agar plate is a single type of bacterium that we have isolated from an enrichment composting experiment, where small pieces of polyethylene terephthalate (PET) cut from a standard PET water bottle had been incubated for several weeks at 50°C (along with some horse manure). The morphology (shape, size, and colour) of this bacterium when it grows as colonies on an agar plate are quite unusual. The bacterial colonies grow in a sort of expanding ring, leaving no apparent growth in the middle.

Two different dilutions of bacteria from a municipal compost heap in Belfast

A small sample of this compost was suspended in water and then diluted in serial steps of 100 fold before spreading each dilution over the surface of agar plates and growing at 65°C. The sample on the left is a 1:100-fold dilution and the sample on the right is a 1:1000-fold dilution. From this kid of analysis we can calculate the total number of different bacteria per gram in the original compost. There are 13.6 million bacteria per gram in this compost. Each individual bacterial colony from the plates that have well isolated colonies, are picked off and grown individually for analysis. From these bacteria we have already found some high-temperature enzymes such as tyrosinase and proteases.

If you compost and want to take part in a home composting experiment, you’ll need:

  • a selection of identical compostable or biodegradable items (see list below)
  • a net bag and clip to securely close it (see guidance below)
  • a plastic milk bottle cap (or similar) and permanent marker pen to identify your items

If you do not use a composter but you're interested in finding out more, please see our Composting Processes page for more information.

1. Choose your experiment items

Select the type and quantity of compostable or biodegradable plastic items from our list that you would like to test. Please only select items that display the following manufacturer information:

  • 'compostable' (only)
  • 'home biodegradable'
  • 'home compostable'
  • 'suitable for home composting'
  • TUV OK Compost 'HOME' certification mark
  • Din Certco 'HOME COMPOSTABLE' certification mark

NOTE: If testing multiple items together please ensure they are an identical type and brand (one type and brand of item per net bag).

2. Prepare your experiment equipment

To make locating your experiment items in your compost easier, please compost your items in a plastic net bag (the kind of net bag used to hold fruit in a supermarket would be ideal). Use a permanent marker pen to identify your items on a plastic milk bottle cap (or similar) and add to your net bag. To test fruit and veg stickers please stick each label on a plastic milk bottle cap first then add to your net bag. Use a permanent marker pen to identify them. You will have the option to upload photographs of your composter and experiment equipment to help us analyse your results. See our Photography Guidelines for more information.

NOTE: Please ensure you use a perforated net bag. This is so a sufficient flow of oxygen, organic waste and microorganisms can come into contact with your experiment items.

3. Create a login account

Create a login account and share a few extra details about what composter you will be using for the experiment, its location in the UK for our Live Composting Map, and your composting method. Please set the duration of your experiment according to how long it usually takes you to make compost. There is the option to share photos of your composter and experiment items and equipment, if you wish. Please indicate on your form if you would like to share your images on the Big Compost Experiment website. See our Photography Guidelines for more information.

4. Start your experiment

Securely close the net bag containing your experiment items and identifying markers and add to your composter. Carry on composting as usual. We'll send you an email reminder when your experiment is due to finish and it's time to look for your net bag and items.

5. Submit your results

When your experiment timer has finished, please look for the net bag and items in your compost. You can use a trowel, spade or household sieve to locate it. Under 18s must be accompanied by a responsible adult. Check the contents of your net bag for any traces of your items. If there are any traces please compare them with our 'Scale of Degradation' in the results form in your login account and share any other useful observations about your experiment. There is the option to share a photo of your results. Please indicate on your form if you would like to share your image(s) on the Big Compost Experiment website. See our Photography Guidelines for more information.

NOTE: Once you have completed your experiment, please dispose of any item remains in your general waste collection. Check locally for recylability of other experiment equipment and rinse before recycling.

How to take a photograph of your experiment equipment

Pre- and post-composted items and equipment

  1. Place your biodegradable or compostable items on a clean surface alongside any secondary packaging (if applicable) and net bag. A contrasting surface is preferable (i.e. one on which the items will stand out).
  2. Orientate items and packaging (if applicable) in order to capture any compostable labelling or certification marks (if displayed). If testing multiple items together please ensure they are an identical type and brand (one type/brand of item per net bag).
  3. Position your camera approximately 1 metre above the objects. Position items clearly within the viewfinder of your camera or camera phone, so that all edges of items are visible. Please ensure no recognisable features (people, faces, house number, etc.) are visible in the image.
  4. Take a photograph (while keeping your hand steady!)
  5. Upload photographs via your login account, with the option to display them on our Gallery page.