We are all increasingly aware of the extent of humanity’s impact on Earth. The increasing concentration of atmospheric greenhouse gases and Earth’s changing climate are constant in our news, but there are other ways that humans are directly impacting the environment. Production of food is vital for society, but finding sustainable and environmentally friendly methods of feeding everyone must be a priority.
Dr. Agnieszka Latawiec from Pontifical Catholic University of Rio de Janeiro and co-founder of the International Institute for Sustainability in Brazil is particularly interested in improving the management of pasturelands.
Read more about her research here: www.nature.com/articles/s41598-019-47647-x
Hello and welcome to Research Pod. Thank you for listening and joining us today. In this episode we will be looking at sustainable agriculture in Brazil. Dr Agnieszka Latawiec’s research is particularly focussed on the effects of biochar on pastureland productivity and whether it is an economically viable method of improving the quality of soil.
We are all increasingly aware of the extent of humanity’s impact on Earth. The increasing concentration of atmospheric greenhouse gases and Earth’s changing climate are constant in our news, but there are other ways that humans are directly impacting the environment. The production of food is vital for society, but with a population expected to reach over nine billion by 2050 finding sustainable and environmentally friendly methods of feeding everyone must be a priority. Dr. Agnieszka Latawiec from Pontifical Catholic University of Rio de Janeiro and co-founder of the International Institute for Sustainability in Brazil is particularly interested in improving the management of pasturelands
So what are pasturelands?
Pasturelands are used for grazing livestock, such as horses and cattle. 26% of the ice-free lands on Earth’s surface are pasturelands, which provide food for commercial cattle herds that meet the rising global demand for meat. Within Brazil alone, herds of cattle are farmed on approximately 158 million hectares of pastureland, and the country contains the world’s largest commercial cattle herd. The soils that support these pastures are often degraded, with a low carbon content and increased acidity, along with a poor ability to retain water and decreased nutrients. Low productivity soils often force farmers to deforest surrounding land to move cattle to better quality pasture, which has historically led to widespread deforestation in Brazil and a subsequent loss of biodiversity. The rainforest in South America is also a large and vital carbon sink, drawing down carbon dioxide from the atmosphere and helping to mitigate climate change. The majority of deforested land in Brazil has been replaced with low-productivity pastureland, of which over 70% is classed as degraded.
While the picture may appear a little gloomy, governments, scientists and farmers alike are working hard to address the issue in a variety of ways, with either exciting new technological developments or by improving established farming practices. Brazil is the second-largest producer of meat in the world, and demand is expected to continue rising. This makes identifying sustainable and environmentally friendly farming methods a priority. Preventing further deforestation is vital, and so the focus is on improving the productivity of pasturelands already in existence in a sustainable manner.
One of the potential methods of improving the quality of pastureland soils is with the use of biochar. This charcoal-like substance is made by burning organic material using a method called pyrolysis. Biochar is rich in carbon and very stable, and can be easily mixed into soils. Organic materials such as wood residues or dead plants are burnt in a specific design of kiln in low oxygen conditions. Biochar has actually been used for thousands of years, and it is thought the modern-day methods of production are based on practices used by ancient Amazonians.
Why is biochar good for soils?
It is well established that biochar has a positive effect on soil health to varying degrees depending on the context. Due to its porous nature, it may improve the water retention of soils as well as acting as a water filter. It may also improve soil pH by lowering acidity. Biochar is often accompanied by ash that is rich in nutrients, such as potassium and phosphorus, that will support healthy plant growth. Dr Latawiec and her colleagues completed trials where they studied the effects of biochar on the harvests gathered from greenhouse pot trials and field studies. They mixed biochar into Brazilian pastureland soil and grew two species of commonly used grass to investigate the impact of biochar on plant yield in addition to soil health.
The team noticed increased productivity in the pasture soils along with an improvement in some soil properties. The soil became less acidic, and nutrients such as potassium increased in content. The team also discovered that using additional fertilisers helps to maximise the effects of biochar, suggesting that a regime of the two combined could produce optimum results. They saw an increase in plant yield for one of the study species (Brachiaria) but not for the other (Panicum), indicating that the effects depend on the plant species.
Why is biochar so good for the environment?
Scientists are particularly interested in the use of biochar as a sustainable method of reversing soil degradation in preparation for farming intensification because it can also sequester carbon. Humans have increased the atmospheric carbon dioxide levels very rapidly since the Industrial Revolution, with levels reaching 415 parts per million in 2019. This dramatic increase is causing global climate change, with temperatures expected to rise between 1.5 and 2 degrees over the next few decades. Scientists and policy makers are hoping to address the increasing carbon dioxide in a variety of ways, such as increasing the amount that is drawn down and stored from the atmosphere.
Plants absorb and store carbon dioxide from the atmosphere as part of photosynthesis. When they die, they decompose and this releases carbon back into the atmosphere as carbon dioxide. The creation of biochar provides a method of storing carbon more permanently. Rather than letting waste biomass decompose, the pyrolysis process that forms biochar ‘locks’ the carbon that was in the plant into its structure, preventing around half of the carbon from being released into the atmosphere as carbon dioxide. The presence of biochar within soils also naturally increases the amount of carbon that can be held within the soil, improving its ability to act as a carbon sink.
Dr Latawiec and the team noted that an invasive plant species such as Gliricidia sepium, found in Brazil, makes an ideal candidate for biochar. Branches of Gliricidia sepium must be regularly cut back to maintain control and avoid unwanted shade, providing a large amount of waste organic material. Collecting it for biochar not only reduces the amount of carbon dioxide released back into the atmosphere – it also helps prevent this invasive species from spreading into native vegetation.
The team was able to calculate that for each hectare that had biochar added to the soil, 13 tonnes of carbon dioxide was sequestered into the soil. A further 91 tonnes were saved due to land sparing; by increasing productivity in the soil, sections of land are no longer required for pasture and can be used for other purposes, for example reforestation. The Brazilian Native Vegetation Protection Law requires farmers to spare land for conservation, so successfully improving the quality of pastureland soils may mean farmers have less need to deforest native vegetation, reducing carbon dioxide release to the atmosphere.
But is biochar cost effective?
Whilst biochar has clear benefits for the environment and may provide a sustainable method for intensifying farming on degraded soils, there have not been many studies looking at the cost-effectiveness of biochar’s use. The costs of biochar production must be taken into account, along with its purchase costs. Dr Latawiec and her team completed a cost-benefit analysis for the use of biochar by Brazilian smallholder farmers.
The creation of biochar is relatively simple and does not require the installation of expensive or complex equipment, which is why it is often viewed as a low-cost method for improving soil quality. However, the team were able to take into account the labour costs that are involved in the production of biochar, and found that it is not competitive when compared to other methods of soil recovery. The increase in productivity and subsequent meat production after biochar was applied would not be enough to outweigh the cost of production. The team identified that biochar is 617% more expensive than other common fertilisers, making it an unviable approach for smallholder farming.
There are some alternatives which could help reduce costs. These include using commercially produced biochar, applying biochar at lower doses or using biochar in a more profitable farming context. Given the additional benefits of biochar use such as carbon sequestration, farmers could also benefit from Payments for Ecosystem Services to leverage the costs and contribute to global goals to combat climate change. If payments for carbon were used to subsidise biochar use, the carbon price would need to range from 53.09 to 78.72 US dollars. This is compatible with the range required to achieve the goals of the Paris Agreement. As biochar may contribute to a reduction in greenhouse gases, ‘Low Carbon Agriculture’ funding could also be used to encourage uptake.
So, what is the future of biochar?
It is possible that biochar could provide a sustainable and environmentally friendly approach to improving soil quality if the costs of production could be subsidised.
The use of biochar remains an excellent technique for addressing the degradation of soils, but further research is required to determine in what scenarios its production costs are outweighed by its benefits. The team note that further study is required to understand the full range of effects that the use of biochar has in soil quality and productivity. It is likely that biochar will be only one small part of a range of solutions that will provide environmentally friendly and sustainable sources of food for future populations.
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