Biochar facts for kids
Biochar is a special type of charcoal made for use in soil. It looks like a light, black material left over after heating plant matter, called biomass, without much oxygen. It's mostly made of carbon and ash. Even though it has "bio" in its name, biochar doesn't have living things in it right after it's made. It only gets helpful microbes when it mixes with soil or other living environments.
People mainly use biochar in soil to make it healthier. It helps the soil breathe better, reduces harmful gases from the soil, and stops important plant nutrients from washing away. Biochar can also make acidic soil less sour and help sandy soils hold more water. Using biochar can make soil more fertile and help crops grow better. But, using too much biochar or the wrong kind can sometimes cause problems. It might harm helpful soil creatures, reduce water in some soils, change the soil's pH, or make it too salty.
Besides helping soil, biochar has many other uses. It can be part of a farming method called slash-and-char, which is better for the environment. It also helps soil hold water and can even be added to animal feed. Scientists are also very interested in how biochar can help fight climate change. Because biochar is very stable, it can stay in soil for thousands of years. This idea led to biochar carbon removal, which is a way to store carbon safely in the form of biochar. This carbon storage happens when good quality biochar is put into soil or mixed into building materials like concrete.
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What Does "Biochar" Mean?
The word "biochar" was created in English in the late 1900s. It comes from two parts:
- The Greek word 'βίος' (bios), which means 'life'.
- The word 'char', which is another name for charcoal made from plant material.
So, "biochar" means charcoal that takes part in living processes. This includes processes in soil, water, and even animal stomachs.
A Look Back: Biochar's History
Long ago, before Christopher Columbus arrived, people in the Amazon rainforest made a type of biochar. They would slowly burn farm waste, like old plants, in pits or trenches. They covered the burning material with soil to make it smolder. We don't know if they knew this biochar would make their soil better for farming. European settlers later called this special soil terra preta de Indio, which means "black earth of the Indians." Scientists now think that a type of Amazonian earthworm helped mix this charcoal into the soil.
How Is Biochar Made?
Biochar is a fine, black material rich in carbon. It is made through a process called pyrolysis. This means heating plant material, or biomass, at high temperatures without much oxygen. This stops the material from burning completely. Pyrolysis creates three main things:
- A solid material: biochar.
- A liquid: bio-oil.
- A gas: syngas.
Making Biochar with Gasifiers
Many biochar products sold today are made using machines called gasifiers. The gasification process has several steps. It involves heating biomass to very high temperatures, from 250°C to 1000°C, in different zones. The exact amount of biochar produced depends on things like the temperature and how long the material is heated.
If you want more biochar, you use temperatures around 400-500°C. Higher temperatures, above 700°C, create more liquid and gas fuels instead. Pyrolysis happens faster at higher temperatures, taking seconds instead of hours. A typical process might yield 60% bio-oil, 20% biochar, and 20% syngas. Slower heating can produce more biochar, about 35%, which is great for soil. These processes also create energy.
Unlike the ancient Amazonian method, modern large-scale systems capture the liquid and gas products. This prevents harmful gases like carbon dioxide and black carbon from going into the air. These systems can process farm waste, paper waste, and even city waste. Some systems can even collect clean drinking water during the drying stage!
Simple Ways to Make Biochar
Farmers in many parts of the world can make their own biochar easily. They gather crop waste, like corn stalks or rice straw, into piles. They light the top of the pile and then put out the embers with dirt or water. This method, called a "top-down burn," creates much less smoke than traditional burning.
Larger, more industrial methods can also be used on a smaller scale. Instead of bringing all the plant waste to one big factory, a special truck with a pyrolyzer can travel to different farms. This truck makes biochar right on the farm. The truck uses the syngas it produces for power. The biochar stays on the farm, and the liquid fuel is sent to a storage site.
Companies in places like North America, Australia, and England sell biochar or machines to make it. In Sweden, biochar is used in city tree planting to help trees grow better.
What Plants Are Used for Biochar?
Many different plants can be used to make biochar. These include various types of trees and special plants called energy crops. Some energy crops, like Napier grass, can store a lot of carbon very quickly.
When plants are grown for other purposes, like food, their leftover parts can be used for biochar. For example, Brazil produces a lot of sugarcane. The tops of the sugarcane plants, which are often burned, can be used to make biochar and energy. This could turn millions of tons of waste into useful products. However, some plant leftovers should stay in the soil to keep it healthy.
What Makes Biochar Special?
The way biochar is made and the plants used affect its features. These features are important for how well biochar works for different uses. Scientists have ways to test biochar's properties. These include its chemical makeup, how acidic or basic it is (its pH), and how many tiny holes it has (its porosity).
The temperature used during production changes biochar's structure. Lower temperatures (around 450-550°C) create a less organized carbon structure. Higher temperatures turn this into strong, flat sheets of graphene. Biochar also becomes better at conducting electricity as the production temperature increases. For capturing carbon, higher temperatures make biochar more stable and long-lasting.
How Is Biochar Used?
Storing Carbon to Fight Climate Change
Biochar is very stable, meaning it doesn't break down easily. This makes it useful for biochar carbon removal, which is a way to store carbon. It can help slow down climate change. When plants and trees die, they release a lot of carbon dioxide and methane into the air. Making biochar also releases some carbon dioxide, but the carbon that stays in the biochar is very stable.
This stored carbon can stay in the ground for hundreds or even thousands of years. This helps reduce the amount of greenhouse gases in the atmosphere. At the same time, biochar in the soil can improve water quality, make soil more fertile, help crops grow, and protect old-growth forests.
Biochar can store carbon in soil for a very long time, much like coal. Experts say biochar keeps about half of the carbon from the original plant material. It also slows down how quickly carbon breaks down in the soil by a lot. Scientists like James Hansen and James Lovelock have supported using biochar to remove carbon dioxide from the air.
A report from 2010 suggested that using biochar in a smart way could reduce global emissions of carbon dioxide, methane, and nitrous oxide by a huge amount each year. This could be done without harming food supplies or natural habitats. By 2023, the importance of biochar for storing carbon was widely accepted. Studies showed it could store a significant percentage of carbon dioxide emissions in many countries.
Boosting Soil Health
Biochar is very good for unhealthy soils, especially in tropical areas. Its many tiny holes help the soil hold both water and important plant nutrients. Soil scientists have noted that biochar is a great home for helpful microorganisms. When these good microbes are already living in the biochar, it helps soil and plants stay healthy.
Biochar can also stop harmful bacteria, like E-coli, from washing through sandy soils. It can improve crop yields for plants that need a lot of potassium and less acidic soil.
Biochar can make water cleaner, reduce harmful gases from the soil, and stop nutrients from washing away. It also makes soil less acidic and can reduce the need for irrigation and fertilizer. The tiny holes in biochar keep water and minerals in the top layers of soil. This helps plants grow and saves money on fertilizers. Biochar can also help plants fight off diseases and remove heavy metals from the soil.
The effects of biochar depend on its properties and how much is used. Biochar can reduce nitrous oxide emissions by up to 80% and stop methane emissions. Both of these are much stronger greenhouse gases than carbon dioxide.
Studies have shown that biochar helps crops grow better in poor soils. Mixing biochar with compost has also improved soil moisture, crop growth, and quality in several countries. Biochar can be made with specific qualities to help different types of soil. In Colombian savanna soil, biochar helped plants absorb more nutrients and stopped important nutrients from washing away.
Gardeners who want to help fight climate change add biochar to their soil. This increases plant growth, which helps take more carbon out of the air. Using biochar as an additive in animal feed is another way to get it into pastures and reduce methane from animals.
To significantly improve plant yields, about 2.5 to 20 tons of biochar per hectare are needed. In developed countries, biochar can be expensive. However, in developing countries, the main challenges are having enough plant material and time to make it. A good solution is to use smaller amounts of biochar mixed with fertilizers.
It's important to remember that using too much biochar or the wrong type can sometimes cause problems. This includes harming helpful soil creatures, reducing available water, changing soil pH, or making the soil too salty.
Slash-and-Char Farming
Changing from slash-and-burn to slash-and-char farming in tropical areas can help the environment. It can reduce both deforestation and carbon dioxide emissions. It also helps crops grow better. Slash-and-burn farming leaves only 3% of the carbon in the soil. Slash-and-char, however, can keep up to 50% of the carbon.
This change in farming could store a lot of carbon each year. Biochar also reduces the need for nitrogen fertilizers. This saves money and lowers emissions from making and transporting fertilizers. By making soil easier to work with, more fertile, and more productive, biochar-enhanced soils can support farming for a very long time. This is different from slash-and-burn soils, which quickly lose their nutrients, forcing farmers to move to new areas.
Helping Soil Hold Water
Biochar has a very porous structure and a large surface area. This means it is good at absorbing and holding water. As a result, fertilizers and other nutrients stay in the soil longer, benefiting plants.
Animal Feed
Biochar has been used in animal feed for hundreds of years.
An Australian farmer named Doug Pow explored mixing biochar with molasses for animal feed. He believed that biochar could help animals like cows digest food better and reduce their methane production. He also used dung beetles to mix the biochar-infused animal waste into the soil. This helped keep nitrogen and carbon in the soil, reducing harmful gas emissions and improving soil fertility. His work showed that this feed helped Angus-cross cattle gain weight. Doug Pow won an award in 2019 for this idea. His work also led to studies on dairy cattle, which showed less odor and more milk production.
Adding Biochar to Concrete
Making Portland cement, a key part of concrete, uses a lot of energy and creates a lot of carbon dioxide. Cement production causes about 8% of global CO2 emissions. The concrete industry is now using more additives to reduce the amount of cement needed. Biochar has proven to be a good additive. It helps reduce emissions from concrete production while keeping the concrete strong.
Studies found that adding 1–2% biochar by weight is best for concrete mixes. This amount balances cost and strength. A 2% biochar mix has increased concrete strength by 15% in some tests. Biochar concrete also shows promise in resisting high temperatures and reducing water leakage.
Comparing biochar concrete to other additives, biochar showed lower toxicity. This means it's a more environmentally friendly choice.
Biochar as a Fuel Slurry
Biochar mixed with liquids like water or ethanol can create a new type of fuel called biochar-based slurry. This fuel is similar to coal slurry but has the advantage of coming from renewable plant sources. It is becoming a promising fuel in areas where plant material is plentiful and electricity often comes from diesel generators.
Cleaning Water
Biochar is also used to clean water. Its properties, especially its tiny holes, can be changed to make it better at removing pollution. Biochar has been shown to remove harmful substances like heavy metals, dyes, and other pollutants from water.
Ongoing Research
Research into biochar is happening all over the world. Universities like the University of Edinburgh and the University of Georgia are studying it. The Volcani Center and the Swedish University of Agricultural Sciences are also involved.
Scientists are also looking at how biochar can help sandy soils in dry and damaged areas. In Namibia, biochar is being explored to help communities deal with drought and improve their food security. This is done by making and using biochar from local plants. Similar ideas are being explored in Australia for rangelands affected by too many woody plants.
Recently, biochar has gained interest as a way to filter wastewater. It can absorb pollutants like medicines, personal care products, and certain chemicals. In some places, people's interest in biochar encourages governments to support more research into its uses.
What Studies Show
Scientists have studied the long-term effects of biochar by looking at soil in Belgium. This soil had charcoal-rich black spots from charcoal production that dated back before 1870. The study found that soil treated with charcoal for a long time had more carbon from corn plants. It also showed less carbon breaking down, likely because the biochar protected it and helped soil microbes. This study proves that biochar can help store carbon for a long time.
Biochar stores carbon in soils because it stays there for many years, even thousands. It can also help store carbon indirectly by making crops grow better and possibly reducing how quickly carbon breaks down. Lab studies have shown how biochar affects carbon breakdown using special carbon markers.
Studies using advanced analysis showed that adding biochar to soil increased a type of organic matter linked to biochar carbon. This research also found that aromatic carbon built up in specific spots in the soil and mixed with clay minerals. These findings suggest that biochar helps stabilize carbon in soils by slowing down how it breaks down.
See also
In Spanish: Biochar para niños
- Activated carbon
- Charring
- Dark earth
- Pellet fuel
- Soil carbon
- Soil ecology
