Indigenous Charcoal and Biochar Production: Potential for Soil Improvement under Shifting Cultivation Systems

Abstract

Biochar offers potential for enhancing the agricultural productivity of degraded lands in the humid tropics. This paper reports on charcoal and biochar production among peasant farmers who practise shifting cultivation in the Peruvian Amazon. Using wood from secondary forest fallows, farmers produce charcoal for market in earthen mound kilns, also yielding biochar, as charcoal fines, which becomes incorporated into kiln site soils. Data were collected in a riverside community near Iquitos through interviews with farmers/charcoal producers, an inventory of kiln sites, a kiln audit of the charcoal production process, and soil sampling of kiln sites and adjacent paired control sites (depth: 15 cm). Our results indicate that kilns incorporate substantial quantities of biochar into local soils (Ultisols), as much as 30 tonnes each year on 0·4-0·8 ha of kiln sites. Additions of biochar and ash significantly enhance soil fertility by increasing organic C content, raising P and other nutrient concentrations, reducing acidity and exchangeable Al, and increasing soil porosity and friability. Organic C, N, Mg, Ca, and effective cation exchange capacity did not decrease significantly with increasing kiln site age, suggesting that heightened levels may persist for more than a decade after kilns are used. Farmers recognize the elevated fertility of kiln sites and cultivate in them annual and perennial crops, as well as use kiln soil and biochar off-site, in home gardens, nursery beds, and planting holes. Our findings point to the potential of biochar to ameliorate soils and enhance forest recovery under shifting cultivation systems that integrate charcoal production into forest fallow-based rotations.

Cropping history trumps fallow duration in long‐term soil and vegetation dynamics of shifting cultivation systems

“…). Upon clearing a field anew, charcoal is produced in earth mound kilns from a portion of the felled woody biomass (Coomes and Miltner ). A more extensive description of socioeconomics, biophysical setting, and management patterns is given in Coomes et al.…”

“…Average fallow durations between cropping periods range from 3 to 20 years and are positively correlated with household landholdings (Coomes et al 2000). Upon clearing a field anew, charcoal is produced in earth mound kilns from a portion of the felled woody biomass (Coomes and Miltner 2016). A more extensive description of socioeconomics, biophysical setting, and management patterns is given in Coomes et al (2000).…”

Forests as landscapes of social inequality: tropical forest cover and land distribution among shifting cultivators

“…Wood, J. Rhemtulla and O. T. Coomes, unpublished manuscript). Residents have resorted to using biochar to raise land productivity Coomes 2015, Coomes andMiltner 2016).…”

Impact of biochar properties on soil conditions and agricultural sustainability: A review

“…Soil degradation resulting from intensive agricultural use and changing climatic conditions jeopardizes global food security, necessitating the development of novel and environmentally benign technologies that improve soil health and resilience (Gisladottir & Stocking, ). The application of biochar—a carbonaceous material similar to charcoal that is produced by the thermochemical decomposition of biomass under conditions of limited oxygen supply—to soils is one such means of enhancing degraded soils and for mitigating the effects of climate change (Coomes & Miltner, ). Although production of biochar and charcoal consists of the same process, the difference between the two lies mainly in their intended application: When used as a soil conditioner to improve soil quality and crop productivity, the pyrolyzed material is referred to as biochar; when used for energy generation, it is called charcoal (Lehmann, ; Lehmann & Joseph, ).…”