Biomass gasification –smoke less chulas- bio-char in Agriculture

Biomass gasification is a process that converts carbonaceous materials into carbon monoxide, hydrogen and carbon dioxide. This is achieved by reacting the material at high temperatures (>700 °C), without combustion, with a controlled amount of oxygen and/or steam. The resulting gas mixture is called syngas (from synthesis gas or synthetic gas) or producer gas and is itself a fuel. The power derived from gasification and combustion of the resultant gas is considered to be a source of renewable energy if the gasified compounds were obtained from biomass.

The advantage of gasification is that using the syngas is potentially more efficient than direct combustion of the original fuel because it can be combusted at higher temperatures by preventing environmental pollution. Syngas may be burned directly in gas engines, used to produce methanol and hydrogen, or converted via the Fischer–Tropsch process into synthetic fuel. Gasification can also begin with material which would otherwise have been disposed of such as biodegradable waste. In addition, the high-temperature process refines out corrosive ash elements such as chloride and potassium, allowing clean gas production from otherwise problematic fuels. Gasification of fossil fuels is currently widely used on industrial scales to generate electricity.

Biochar is charcoal used as a soil amendment. Like most charcoal, biochar is made from biomass via pyrolysis. Biochar is under investigation as an approach to carbon sequestration to produce negative carbon dioxide emissions. Biochar thus has the potential to help mitigate climate change via carbon sequestration. Independently, biochar can increase soil fertility of acidic soils (low pH soils), increase agricultural productivity, and provide protection against some foliar and soil-borne diseases. Furthermore, biochar reduces pressure on forests. Biochar is a stable solid, rich in carbon, and can endure in soil for thousands of years.

Uses of biochar

1.   Carbon sink

The burning and natural decomposition of biomass and in particular agricultural waste adds large amounts of CO₂ to the atmosphere. Biochar that is stable, fixed, and 'recalcitrant' carbon can store large amounts of greenhouse gases in the ground for centuries, potentially reducing or stalling the growth in atmospheric greenhouse gas levels; at the same time its presence in the earth can improve water quality, increase soil fertility, raise agricultural productivity, and reduce pressure on old-growth forests.

Biochar can sequester carbon in the soil for hundreds to thousands of years, like coal. Such a carbon-negative technology would lead to a net withdrawal of CO₂ from the atmosphere, while producing and consuming energy. This technique is advocated for mitigation of global warming by greenhouse gas remediation.

2.           Soil amendment

Biochar is recognised as offering a number of benefits for soil health. Many benefits are related to the extremely porous nature of biochar. This structure is found to be very effective at retaining both water and water-soluble nutrients. Soil biologist Elaine Ingham indicates the extreme suitability of biochar as a habitat for many beneficial soil micro organisms. She points out that when pre charged with these beneficial organisms biochar becomes an extremely effective soil amendment promoting good soil, and in turn plant, health.

Biochar has also been shown to reduce leaching of E-coli through sandy soils depending on application rate, feedstock, pyrolysis temperature, soil moisture content, soil texture, and surface properties of the bacteria.

For plants that require high potash and elevated pH, biochar can be used as a soil amendment to improve yield.

 Biochar can improve water quality, reduce soil emissions of  greenhouse  gases, reduce nutrient leaching, reduce  soilacidity and reduce  irrigation and fertilizer requirements.  Biochar was also found under certain circumstances to induce plant systemic responses to foliar fungal diseases and to improve plant responses to diseases caused by soil borne pathogens.

Modest additions of biochar to soil reduce nitrous oxide N₂O emissions by up to 80% and eliminate methane emissions, which are both more potent greenhouse gases than CO₂.

It increases yield of crops in degraded and nutrient–poor soils. Biochar can be designed with specific qualities to target distinct properties of soils. Biochar reduces leaching of critical nutrients, creates a higher crop uptake of nutrients, and provides greater soil availability of nutrients. At 10% levels biochar reduced contaminant levels in plants by up to 80%, while reducing total chlordane and DDT content in the plants by 68 and 79%, respectively. On the other hand, because of its high adsorption capacity, biochar may reduce the efficacy of soil applied pesticides that are needed for weed and pest control. High-surface-area biochars may be particularly problematic in this regard; more research into the long-term effects of biochar addition to soil is needed.

Slash-and-char

Switching from slash-and-burn to slash-and-char farming techniques can decrease both deforestation and carbon dioxide emission, as well as increase crop yields. Slash-and-burn leaves 3% of the carbon from the organic material in the soil.

Slash-and-char can keep up to 50% of the carbon in a highly stable form. Returning the biochar into the soil rather than removing it all for energy production reduces the need for nitrogen fertilizers, thereby reducing cost and emissions from fertilizer production and transport. Additionally, by improving the soil's ability to be tilled, fertility, and productivity, biochar–enhanced soils can indefinitely sustain agricultural production, whereas non-enriched soils quickly become depleted of nutrients, forcing farmers to abandon the fields, producing a continuous slash and burn cycle and the continued loss of tropical rainforest. Using pyrolysis to produce bio-energy also has the added benefit of not requiring infrastructure changes the way processing biomass for cellulosic ethanol does. Additionally, the biochar produced can be applied by the currently used machinery for tilling the soil or equipment used to apply fertilizer.

Water retention

Biochar is a desirable soil material in many locations due to its ability to attract and retain water. This is possible because of its porous structure and high surface area. As a result, nutrients, phosphorus, and agrochemicals are retained for the plants benefit. Plants therefore, are healthier and fertilizers leach less into surface or groundwater.

Smokeless chulhas

The cook stoves and the soot that arises from burning biomass — firewood, dung and agricultural residues — are now the focus of a global community fighting climate change as well. The soot — or black carbon — is a killer. It causes respiratory problems and leads to premature deaths. Women and children in poor households are the worst hit. The black carbon particles also contribute to global warming.

The black carbon particles that result from partial burning of fuel live in the atmosphere for not more than a few weeks. In that period, they absorb the visible spectrum of light and consequently warm up the planet. The soot particles are far more dangerous in their intensity of impacting global temperature as compared to carbon dioxide. Uniquely, these soot particles don’t travel so far and cause warming in the region close to their origin. There is greater certainty in the scientific community about this fact. But the scientists are not sure about how the other organic particles — aerosols — that get released during burning, play with global temperatures.

Smokeless chulhas potential to deliver the triple benefits of improved household health and time savings, reduced deforestation and local environmental degradation, and reduced emissions of black carbon, a significant short-term contributor to global climate change. Designing of smoke less chulas meets the following conditions

1.    High fuel efficiency

2.     Low cost durability

3.    Low cost

4.    Mobility and ease of implementation