Biochar - Terra Preta

From the book "Biochar for Home Gardeners - a Guide to Producing, Charging and Applying Biochar to Dramatically Improve Soil and Plant-Health" by Jeff Fry

Biochar Foodweb
The soil food web is the community of organisms living all or part of their lives in the soil. It describes a complex living system in the soil and how it interacts with the environment, plants, and animals.
Biochar increases water-retention, vastly improves the soil's ability to hold onto nutrients and builds healthy soil biology, also known as the soil food web.
Terra Preta biochar soils of the Amazon are thousands of years old.
Biochar of excellent quality can be made at home with rudimentary equipment

Water retention
The addition of biochar to the soil boosts water-holding capacity thanks to its porous structure and its huge surface area. It doubles water retention in loamy sand soil.

How to make biochar
Pyrolysis: thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen.
The Pit and the Kon-tiki Cone Kiln
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The biochar researchers Hans Schmidt and Paul Taylor wanted to show how our ancestors were able to produce large quantities of biochar with apparent ease.
Looking at the observations of Archaeologists who saw biochar deposits in clearly demarcated cone-shaped pits - five feet deep and six and a half feet wide at the top, they began experimenting with smokeless fires in such roughly conical pits.
As soon as a layer of hot coal at the bottom of the pit has been produced, you can gradually – every five to ten minutes or so - add combustible material.
The flames at the top of the fire eat up the oxygen, leaving the deeper layers to outgas and char instead of burning down into ashes as they would with oxygen.
Once the top layer shows a little white ash, it is time to add the next layer while the previous layer continues to burn without oxygen. At the end it has to be quenched with water.A shovel is all you need.

How to crush the biochar
There are several methods of crushing char. My husband uses the shredder and is very happy with it.
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Charging biochar
Adding biochar to your compost is likely the best method for inoculating the biochar with microorganisms and fungi as well as saturating it with nutrients so that it is rich and ready to go when you apply it to your soil. It also helps the composting process.
Biochar also reduces odour and shortens the compost's time to maturity thanks to increased moisture retention and increased microbial activity.

Pee Charging
Charging your biochar with pee is an extremely easy and effective option. Plain biochar in wheelbarrows or buckets will do well, and then all you have left to do is add your pee.
The author lets his become totally soaked, even covered and lets it sit for at least a few days to really let the char become saturated before using it.
Alternatively, pee-charged biochar can be added to your compost pile.