If you do any cooking at all you will be producing some vegetable waste. Even if you only have a small garden, you will have a few plants, and those plants need fertile soil. As we all strive to become more self-sufficient it makes sense to turn your vegetable waste into rich compost for those plants.

Unless you live in a smoke-free zone, having a barbecue is something many of us enjoy. It gets us outside, is a change of scenery and also a great way to entertain.

The ‘cook to compost’ idea allows you to combine these two activities. More importantly it takes all the hassle out of small-scale composting. Traditional composting requires you to add other ingredients to your vegetable waste to allow air to circulate, such as wood chips or small sticks. To soak up the juices that leach out of your compost you can add cardboard or shredded paper. Your Tawi outdoor stove produces high quality biochar which can replace all the ingredients listed above, making the whole process much simpler. There are other advantages to the biochar; your compost will not smell because the biochar is an effective deodoriser. Your compost will take less time to mature as there are no cardboard or woody bits to break down. Of greater importance, adding ‘carbon compost’ to your soil will make it far more resistant to weather extremes. The super adsorbent biochar prevents water-logging or your soil after heavy rain and retains soil moisture during droughts. As our biochar will remain in the soil for decades, it will continue to perform this service for you year after year. 

Equipment you need.

A Tawi stove that is the right size for you. The reason you need biochar from a Tawi outdoor stove is that the majority of biochars you can buy readily are not absorbent or adsorbent enough. Using inferior biochar will not give you high quality compost.

You need a composter. This does not have to be expensive. Again, pick a size that works for your household. The composting bags shown on our website work well for an average household of four.

Fuel for your Tawi outdoor stove.

Ideally you will collect your own fuel. This can be hedge and plant prunings from your garden or fallen sticks and twigs collected off the ground when out for a walk. Prunings need to be kept in a dry place for at least six months to season; think of them as a resource from your garden. Fallen sticks can be used straight away, as long as they are dry.

Collecting your biochar.

After your barbecue, harvest your biochar. You need to let it dry out a little. This can be done by putting it in a pile and protecting it from the rain. Leave it like that for at least a week, then you can store it in a lidded tub. There is no need to crush it up if you have used small sticks for fuel, as the biochar you have made is the perfect size.

Setting up your composter.

Place your composter in a sheltered spot that is easy to get to from your kitchen. Spread a layer about 5cm deep of biochar around the base of your composter. This will soak up any juices that have make it to the bottom of your compost pile. You can then start adding your vegetable waste. Spread this out over the layer of biochar. Keep adding until the vegetable layer is around 8cm deep. Spread another layer of biochar on top until most of the vegetable matter is out of sight. Now add another layer of vegetable waste. Repeat this layering process until you get to the top of the bin. Your last layer should be biochar as this will help insulate the top of the composter. Close the lid of your composter and leave it to mature for at least four months; however, the longer the better.

Harvesting your compost.

Most composters have a door at the bottom because the material you put in first will be ready to use first. Open this door and if you see a lovely dark material that doesn’t have too many recognisable bits of vegetable in it, then your compost is ready to use. Don’t forget that the waste you added to the top of the bin might not be mature enough yet. As you remove your compost from the bottom of your composter you can add more layers to the top. If you don’t have a lot of vegetable waste you might be able to start harvesting compost before you completely fill the composter. If you do reach the top before the bottom layers are mature enough to use, you will need a second composter or a bigger one!

Using your compost.

How it works.

The biochar within your compost will have soaked up all the juices that came out of your vegetable matter as it decomposed. Within these juices are nutrients which the biochar adsorbs onto its surface. These nutrients provide fuel for mycelium and bacteria, which in turn provide food for your plants. In sandy soil your compost will retain water for your plants to use in times of drought. Conversely, in clay soils, your compost will make the soil easier to work and less prone to water logging, protecting your plants from root damage. Unlike peat-based composts, your carbon-based compost will not break down and will keep serving your plants indefinitely. A carbon-based compost, known as terra preta, used in the Amazon basin over 1,000 years ago is mined and sold as compost today.

Use in flowerbeds.

As you remove your compost, some areas will contain more biochar than others. You want to mix it all up. You can now add your compost to your soil. The compost you have made is extremely rich with a very high stable carbon content. This means it stays in your soil for a very long time. Regular compost needs replenishing every year. Your carbon compost will not. Sprinkle a layer of compost over your prepared ground until most of the soil is covered, do not add too much. Mix this layer into the top 10cm of your soil.

Use in pot plants.

For pot plants, put a layer of your compost in the bottom of the pot, no more than 20% of the pot height. This layer will help retain water during dry periods; you should never need to replace it.

If you find you are making too much carbon-compost to use in your own garden, share it with your friends!

Using biochar as a deodoriser.

Tawi biochar is an excellent deodoriser, and not just for your compost; you can use it anywhere in the home. To use it as a deodoriser, place a cup of partially dried biochar in the tote bag that was supplied with your Tawi. Place the bag on a hard surface and spread the biochar around the inside of the bag. Use a mallet or block of wood to break the biochar up until most of it is a powder. Keep this powder in a sealed jar to prevent it from drying out. Sprinkle it into your rubbish bins if they smell. Add some to the compost bin in your kitchen. A saucer of biochar powder in your fridge works wonders with unpleasant odours.

Carbon negative cooking.

The compost you have made is carbon negative. The reason for this is some of the carbon dioxide drawn out of the atmosphere to make the wood you burnt in your Tawi has been turned into solid carbon. This solid carbon will not break down for thousands of years. Tawi biochar is over 90% stable carbon, which is far higher than most biochars. We estimate it takes around 50 meals, cooked on your Tawi, to completely offset the Tawi stove’s carbon footprint (the amount of CO2 released while manufacturing your Tawi).