Background Recurring wildfires on degraded peatlands throughout Central Kalimantan have resulted in severe economic and social impacts for local people along with globally significant environmental impacts. The interdependence between the livelihoods of local villagers and wildfire is not well understood in areas of degraded peat in proximity to urban environments. Aims The aim of the study was to consider fire hotspots in two villages close to the regional capital of Palangka Raya. These were Kalampangan, a Javanese transmigrant farming village, and Tumbang Nusa, a Dayaknese fishing village. Methods A system dynamics model was constructed to study the factors contributing to greenhouse gas emissions and wildfire extent resulting from long-term peatland degradation. The model was used to analyse existing policy scenarios where degraded peatlands are cultivated in perpetuity, and then consider hypothetical future policy scenarios where efforts are made to rewet and rehabilitate peatland while alternative livelihoods are enabled. Conclusions Analysis reveals that the assumption within the model of unconstrained alternative livelihoods is insufficient to facilitate full rewetting where the incumbent livelihood is reliant on drained peatland. Implications Only when livelihood alternatives displace drained peatland cultivation is full rewetting and sustained reduction in fire risk achievable in both villages.

Biochar has been lauded for its potential to mitigate climate change, increase crop yields, and reverse land degradation in tropical agricultural systems. Despite its benefits, confusion persists about whether the use of biochar is financially feasible as a soil ameliorant. A comprehensive review of previous studies of biochar's financial feasibility was performed (33 relevant publications). Financial performance appraisal (US$ Mg−1 biochar) and greenhouse gas abatement cost estimates (US$ Mg−1 CO2e) were used to gauge the financial feasibility of the biochar scenarios within each publication. Ordinary least squares multiple linear regression was used to evaluate the predictive capacity of scenario financial feasibility as dependent on variables including national income levels, climatic conditions, pyrolysis technology scales, and pyrolysis capabilities. Analysis revealed that scenarios where biochar was applied targeting yield increases in high‐value crops in tropical locations with low incomes and biochar‐focused small‐scale production, were overall significant predictors of biochar scenario financial feasibility. We find that the average abatement cost of biochar applied in ‘lower‐income countries’ is −US$ 58 Mg−1 CO2e (financially feasible) compared with +US$ 93 Mg−1 CO2e in ‘higher‐income countries’ (not financially feasible). Climate policies of lower‐income countries in tropical climates should consider biochar as an input for small‐scale climate smart agriculture to address land degradation in tropical agricultural systems. Based on recent evidence it is suggested that biochar fertilizers, a value‐added biochar product, could present a commercially feasible pathway for biochar value‐chain development in higher‐income countries.

The use of biochar in avocado orchard soils has not yet been investigated in rigorous scientific experiments. We determine the effect of wood biochar on avocado growth, fruit production and economic benefit. Biochar was applied at 0%, 5%, 10% and 20% volume by volume basis. Biochar significantly improved the growth of avocado seedlings and increased fruit yield in the first three years after planting. There was an overall increase in soil carbon, fruit yield, tree diameter and height in all biochar treatments relative to the control over the seasons. Trees planted with biochar had 18-26% greater growth rates (in terms of height and stem diameter) than the control. Tree diameter was significantly greater with biochar (145.4 +/- 3.3 mm) relative to the control treatment (125.0 +/- 2.7 mm). Tree height was also significantly greater with biochar (3.7 +/- 0.1 m) relative to the control treatment (3.4 +/- 0.1 m). The fruit count from the biochar row was significantly greater (97%) in 2018. Heavy bearing trees typically have a lower yield in the subsequent year but despite this, the 2019 fruit counts were higher in aggregate for the biochar amended trees (20%) relative to the control. A cost-benefit analysis indicated that if yield surplus of fruit trees continued for three years, and assuming avocado prices remain at similar levels, then the discounted net benefit over a hectare would amount to US$8581, or US$105 per metric tonne of biochar applied.

Oil palm waste from South Sumatra may represent an abundant source of biochar for beneficial agronomic use in Australian broad-acre farming systems. Here a cost–benefit analysis and carbon footprint of biochar applied to three different Australian broad-acre crops are presented, covering application rates of between 1 and 40 Mg ha−1 and considering either the effect of the biochar on yield or the effect of the biochar on reduced fertilizer requirement. Yield and nutrient efficiency effects are assumed to be constant across all crops. Analysis reveals that empty fruit bunch biochar could be produced in South Sumatra and transported to the farm gate in Australia at a minimum acceptable sale price per Mg of USD $266 to the biochar manufacturer. Despite assumed uniformity of the biochar effect, the return on investment for the biochar user from the perspective of yield increase varied significantly by crop (sugarcane: 67% return on investment [ROI], irrigated cotton: 43% ROI, dry land cotton: −22% ROI, wheat: −72% ROI). The study found that the average carbon footprint in CO2e over 100 years was −691 kg Mg−1 biochar when used to influence crop yield, and −286 kg Mg−1 biochar when used to reduce fertilizer requirements.