Biochar for Climate-Friendly Agriculture: Assessing the Potential for GMS

April 12, 2017

This biochar assessment project aims to evaluate the potential application of biochar technology in the Greater Mekong Sub-region (GMS). The project included all GMS countries, i.e. Cambodia, Lao PDR, Myanmar, Thailand, Viet Nam and Yunnan Province and Guangxi Zhuang Autonomous Region of the People’s Republic of China (PRC).

Biochar is the carbon rich product produced when biomass such as  wood, manure or leaves, is heated with little or no available oxygen. The production and application of biochar into the soils offer multiple potential benefits. Biochar stores organic carbon in the soil on a millennia scale thus providing climate change mitigation benefits. There are significant soil improvements such as releasing nutrient elements, reducing nutrient leaching and gaseous losses, reducing soil acidity, increasing water holding capacity, and improving the soil fauna or soil biological function. The production of biochar provides an efficient and renewable energy source and Biochar production provides a sustainable solution for the management of green waste.

Land suitability for biochar application.  The benefits of biochar application to soil, in terms of crop productivity, can be maximised by selecting the right soils to which biochar can be  added. For the GMS, biochar suitability of soils was determined based on soil properties, e.g. pH, percent base saturation, texture, soil depth and slope steepness. Soil properties,  percentage of slope and land use information were used to rank agricultural land into biochar suitability classes. Three biochar suitability classes, i.e. land with low, medium and high suitability, were created and a biochar suitability map was produced with these classes for the GMS.

About 25% of the soils in the GMS are mostly Cambisols, Fluvisols, Gleysols and Luvisols. These are the key agricultural soils of the region. The inherent fertility of these soils varies from low to moderate in most cases. Some soils from the Fluvisols and Gleysols groups may have moderate to high fertility.

Potential ‘Priority Areas or Hotspots’ for Biochar Application in the GMS.  Based on the biochar application suitability of the agricultural land, potential biomass availability and ADB economic corridors, two to four biochar hotspots have been identified in each of the GMS countries.
• These sites are located close to the transport corridors and a significant amount of crop residues and animal waste are potentially available in the selected areas.
• The identified locations are:  Svay Rieng and Kampong Chhnang provinces in Cambodia; Vientiane and Savannakhet provinces in Lao PDR; Nay Pyi Taw Council and Shwe Bo district in Myanmar;  Rayong, Kalasin, Nakhon Pathom and Nakhon Ratchasima provinces in Thailand; Tay Ninh, Vinh Phuc, Binh Thuan and Binh Dinh provinces in Viet Nam; and Luliang County in Qujing
district in Yunnan Province and Yongning, Gangbei and Xingbin districts in Guangxi province in the People’s Republic of China (PRC).

Availability of agricultural and animal waste for biochar production: More than 104 million tons per annum of agricultural residues can be sustainably removed from agricultural land for biochar production. The agricultural residues are predominantly based on rice production with the contribution of waste from rice cropping varied from 51 – 84% in the GMS countries.  Animal wastes are enriched with essential plant nutrients and could be useful feedstock alone or additive to crop residues for biochar production. Based on the total number of livestock and poultry animals in the GMS countries, it is estimated that approximately 294 million tons of dry animal waste is generated annually. Due to the scattered presence of both agricultural residues and animal wastes, the major challenge is in the collection of these wastes for biochar production. There is significant competition from other users for both types of waste material in the GMS, e.g. for biogas and bio-energy production and other uses. Detailed economic and environmental analysis comparing various uses should be undertaken for selected areas in the GMS.

Assessment of agricultural waste for biochar production and other competing uses and practices: Rice husk is perhaps the single most important agricultural waste that could be used as a feedstock for biochar production. Approximately 1.8 million tons of rice husk can be available for biochar production at the identified hotspots in the GMS. The conversion of rice husk into biochar has a potential to reduce over 1 million tons of CO2 in the atmosphere. Additionally, the rice husk biochar can reduce the consumption of P and K fertilizers by 20 and 100%, respectively.  The potential of rice husk biochar to reduce the ‘ N ‘ fertlizer is only 4%; however, this can be significantly increased if biochar is produced by mixing animal manures with rice husk. It may be noted that a significant amounts of rice straw is burned in open fields, which has serious consequences for the local and regional air quality as high levels of particulate and gaseous toxic compounds are released in the atmosphere. An assessment of the economic viability and carbon abatement potential of straw for biochar production via pyrolysis process with that of bioenergy production by straw briquetting and straw gasification showed the net present value of all three options were negative or unprofitable.The inclusion of local and national subsidies for avoided straw burning and bioelectricity program had significant effects on the by straw briquetting and straw gasification with both these options becoming profitable. However, the outcome for biochar production via pyrolysis process remained negative or unprofitable. Biochar production via pyrolysis process option will break even when biochar is priced at $206 Mg-1, if there are no subsidies in place.
• The total CO2-e abatement potential of biochar can be more effective than bioenergy production by straw briquetting and straw gasification options if indirect contributions (such as by reduced nitrous oxide emission and improved fertilizer efficiency) of biochar are considered in the modelling.