Biochar, a climate action that anyone can take

When buried in the soil, biochar is an easy means to sequester carbon and so mitigate some of our green house gas emissions.

That our climate is rapidly changing ought to be clear to everyone now. Scientific analysis provides clear and sufficient evidence that the increasing frequency of extreme weather events, is caused largely by our burning of fossil fuels and removal of carbon sinks including forests.

The issue is not why is it is occurring or how we got to this stage of chaos.

No, the issue is: what can we do about it?

‘We’ means you and I, not just our national or local governments.

The need to take action is now urgent.

An analysis of data from the Global Carbon Project, has concluded that the world has only five years left before the IPCC(1) carbon budget(2) for 1.5°C of global warming above pre-industrial levels, is blown.

To express that another way: if the current rate of carbon emissions continues, there is a 2 in 3 chance that sometime in 2021, the mean global average temperature will reach 1.5°C of warming above the internationally agreed baseline of pre-industrial levels.

The forms of action that we need to take are clear.

The first is to reduce our carbon emissions immediately. That is, reducing individual emissions from travel (especially vehicles fuelled by fossil fuels), waste disposal, electricity, gas and coal use, and food production and distribution.

Another worthy action is to lobby government to either introduce a carbon tax, or strengthen the emissions trading scheme so that the country’s gross green house gas emissions(3) are reduced.

Doing these things will slow the rate of global warming but will not stop it dead.

So the second necessary action is to remove carbon from the atmosphere.

Planting trees is one way to achieve that outcome, and is the preferred net emissions reduction strategy of this government.

Another way is to sequester carbon where it can be locked away for a very long time.


That can be achieved by manufacturing biochar from waste organic materials like at municipal landfills (domestic waste), and forestry (tree waste), horticultural (crop waste) and animal (e.g. chicken) waste.

These are waste streams which, if they are not pyrolysed and buried, would decay quickly and add to our green house gas emissions.

Pyrolysis (derived from the Greek ‘pyro’ meaning fire and ‘lysis’ meaning separating) is a process of heating organic materials in the absence of oxygen. The process changes the chemical and physical structure of waste organic materials to produce charcoal.

Turning charcoal into biochar is a process of inoculating the char with beneficial bacteria and fungi.

A very efficient way of achieving that is to use it first as animal bedding in the dairy, equine or poultry industries.  Or it can be used as a water filter in waste treatment systems, added to compost or soaked in a tea made from compost or worm farm castings.

Biochar is a soil amendment that realises significant benefits to the soil and thus the crops we grow.  Biochar achieves this by replacing the need for fertilisers that require fossil fuels in their manufacture and distribution.  When buried in the soil, it is an easy means to sequester carbon and so mitigate some of our green house gas emissions.


(1) IPCC: The United Nation’s Intergovernmental Panel on Climate Change is an internationally accepted authority on climate change, and was established to assess the scientific, technical and socio-economic information relevant for the understanding of the risk of human-induced climate change.

(2) In it’s 2014 Fifth Assessment Report (AR5), the IPCC argued, with high confidence, that “Without additional mitigation efforts beyond those in place today … warming by the end of the 21st century will lead to high to very high risk of severe, widespread and irreversible impacts globally.”  The IPCC’s goal is to limit global warming to less than 2.0 °C but preferably to less than 1.5 °C by 2100. This lower limit equates to an atmospheric concentration level of 430 ppm CO2-equivalent.
How this relates to New Zealand is covered in a separate report by the NZ Climate Change Centre.

(3) Gross greenhouse gas emissions are defined as the total emissions from the four defined sectors of Agriculture, Energy, IPPU (Industrial Processes and Product Use) and Waste. Net emissions are the gross emissions plus or minus the emissions or removals from the LULUCF (Land Use, Land-Use Change and Forestry) sector.  When forests are being planted, carbon is being sequestered which subtracts from the gross emissions to yield the net figure.

Governance for Sustainability

Only a little off-topic is this scientific exploration of governance issues in an increasingly complex society.

The topic became clearer to me when I landed on step 8 – Governance Styles – Typical Characteristics (10 clicks of the mouse) that contrasted the characteristics of three different approaches to how we govern social enterprises.


Waste sustainability through composting

Of the four sustainability issues we individually can do something about (energy, food, waste, water), there is one that almost everyone can take action on today and every day.

So easy it is to put your domestic waste in to the rubbish bin each week and see it disappear. Out of sight and out of mind? No, not at all! And nor should it be.

We see our rubbish dumps growing from the unwanted detritus of a consumer society. We smell decaying organic matter as it putrefies away. We hear the big trucks transporting huge quantities of waste around the city and country side.

In 2010, Aucklanders sent over one million tonnes of waste to landfill with around 20% of that being organic waste that could have been diverted from landfill sites.

To enable that diversion, Auckland Council initiated a waste minimisation program that aims to avoid the social, environmental and economic impacts of excess waste.

A major part of that initiative is the composting of domestic organic waste streams as a simple way to divert waste from landfill.

Easy composting method makes for an easy sustainable waste management process.

Composting at home is one part of that program.

Why make compost?

Composting your kitchen and garden wastes turns the nutrients, minerals and organic matter in those wastes, in to a resource for your garden.

The first reason to make compost is that it saves you money by retaining soil moisture levels and avoiding the need to apply fertilisers. Compost replaces the soil nutrients and minerals depleted when crops are harvested and adds organic matter to the soil.

It also sequesters atmospheric carbon in the soil, reducing the release of carbon dioxide and methane gases from landfill to the atmosphere. So the second reason to compost, is the reduction in greenhouse gas emissions that contribute to global warming and hence, climate change.

Who can compost?

Anyone can – just choose a system that is appropriate to your site, your waste types and the amount of waste you create.

Those with a garden and sufficient volumes of waste can install a compost bin to manufacture a beneficial garden resource. A worm farm that converts the same range of wastes to vermicast is better suited to smaller gardens or those with small waste volumes. For those living in an apartment without access to a garden, a Bokashi system achieves the same result – the conversion of wastes to a useful resource.

When to compost?

All the time. Year round, your composted kitchen and garden wastes are an accumulating resource that will save you money.

What to compost?

It is easier to define what not to compost than it is to list what can be composted.

Don’t compost meat, bones and fish scraps as these may attract pests that you do not want around the garden. The Bokashi composting system can handle these scraps but I find there is too much competition for kitchen scraps to use this system. Those who live in an apartment where access to a garden is not easy, will find the Bokashi system ideal for all of their kitchen wastes.

Inadvertently spreading pests and diseases around your garden can be avoided if diseased plants and the seed heads of perennial weeds are not added to the compost. Likewise manures from your domestic pets (dogs and cats mainly) are best not added to compost, especially if the compost is to be applied to food crops.

Foods that may contain pesticide residues, for example banana skins, or are allelopathic, are best kept out of the compost. Allelopathic crops (for example black walnut leaves) exudes chemicals that inhibit germination or growth of other organisms).

Finally, petroleum based machine oil or chain oil ought be avoided.

Otherwise, compost everything, including small amounts of paper and cardboard.

How to compost

Instructions on purchasing or creating your own bin compost, worm farm or Bokashi system can be found at our household composting page.

Composting has so many advantages that it is an integral part of our communal food gardens project.