This article in Phys.org shows an interesting application of using biochar as the soiless medium/substrate for growing tomatoes. By recycling the tomato plants, all parts of which, one can continue to grow tomatoes indefinitely. Excerpt:
“The properties of biochar produced from tomato crop green waste were generally as would be expected,” the authors said. “Tomatoes grown in substrates containing or consisting entirely of biochar did not differ significantly in terms of growth, yield, or fruit quality to those grown in pine sawdust.” The researchers said substrates containing or consisting entirely of biochar also exhibited “acceptable” water-holding and aeration characteristics.
“The results of our study support the concept of creating a closed loop system whereby biochar produced from tomato crop green waste is used as a substrate for soilless, hydroponic tomato production,” said the scientists.
They added that biochar used as a soilless substrate could have considerable advantages for greenhouse tomato growers. “For example, turning tomato crop green waste to biochar would divert 10-60 t·ha-1 of green waste away from landfill each crop cycle. If the assumption is made that the green-waste biochar is produced at 550 °C, it would meet 13% to 50% of the grower’s substrate requirements, on a per-hectare basis.”
Read more at: http://phys.org/news/2015-12-biochar-suitable-substrate-soilless-hydroponic.html#jCp