Eco-friendly production of biochar via conventional pyrolysis: Application of biochar and liquefied smoke for plant productivity and seed germination

Abstract Conventional pyrolysis of agricultural wastes may emit considerable amounts of greenhouse gases that affect negatively the surrounding environment. A trial was done to capture the emitted gases through connecting a small water jacket with the pyrolysis unit. This plant was then used for production of biochars from two waste materials i.e. nutshell (NS-BC) and date-palm seed (DP-BC). The biochars manufactured from the aforementioned waste materials were then evaluated for their applicability vs pig manure (each amendment was applied at rates of 1, 2.5, 5 and 10%; w/w) to improve growth of Brassica chinensis grown on a sandy soil under greenhouse conditions. Collected liquefied smokes were also tested for enhancing germination of Lactuca sativa (lettuce) seeds using different concentrations (0%–5%, v/v). Results revealed that produced biochars decreased significantly soil pH where the highest reduction (14.30%) was occurred due to addition of 10% DP-BC. Moreover, NS-BC and DP-BC decreased significantly soil salinity from 0.21 dSm −1 (control) to 0.13 and 0.14 dSm −1, respectively; on the other hand, pig manure raised significantly soil salinity (10% application rate). Residual organic matter was higher in biochar amended soils than its corresponding values in pig manure treated ones. Generally, all investigated amendments improved considerably the uptake of nitrogen, phosphorus, and potassium. Moreover, they increased chlorophyll pigments in leaves and enhanced plant growth parameters upon their application at rates up to 2.5% with superiority for NS-BC versus DP-BC. Liquefied smoke also improved lettuce seed germination and growth, but only up to 0.25% application rate. Our results highlighted the success of the adopted technique for recycling NS and DP wastes and sustaining the environment.