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# Biomass

Biomass is defined as the total organic matter in a given area or volume of the aquatic and terrestrial systems at a given time.

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## Biomass within the ecosystem

Biomass within the ecosystem can be hard to measure due to varying amounts of water within different living organisms. The amount of carbon/dry mass present within the organism can only be measured when it is deceased.

Biomass is measured in grams per square meter () in terrestrial environments such as grassland. Volume sampled in an aquatic environment is measured in grams per cubic meter ( ).

You will most often encounter biomass expressed as the net change. The equation for this is:

### Biological pyramid of biomass

Like the food pyramid, the pyramid of biomass will include producers and consumers. Instead of showing the movement of energy through the trophic levels of a food chain/web, the pyramid of biomass shows the energy movement within a given area and given time.

Producers are organisms that generate organic molecules, such as glucose, by photosynthesis.

Consumers are defined as organisms that feed on consumers to gain energy. Examples include animals, such as cows and pigs.

Biomass pyramids indicate the relations between different trophic levels and their quantification. The energy is calculated from the dry mass of living organisms.

Fig. 1 - Biomass pyramid in an ecosystem

Calorimetry

The chemical energy stored within the biomass (dry mass) can be estimated using a calorimeter.

Calorimetry can be defined as the process of measuring the amount of heat released and absorbed during a reaction. Calorimetry can determine if the reaction is endothermic (absorbs heat) or exothermic (releases heat).

The calorimeter is used to measure the heat involved in this process. More specifically, a bomb calorimeter will be used to measure the heat released from a specific biomass sample. Bomb calorimetry is carried out in the following steps:

1. A sample (liquid or solid) that can be combusted is weighed.
2. The sample is blazed into a "bomb" vessel.
3. The vessel is filled with oxygen which ignites the sample, and it will start to burn.
4. The temperature increase in the vessel is measured as a calorific value (CV). This value can be calculated by comparing the number with previous sample combustions of a known substance.

## Types of biomass used in the renewable fuel industry

You will often come across a slightly different definition of biomass within the renewable fuel sector. Biomass can also be referred to as a renewable and sustainable fuel source derived from organic matter (wood, crop, animal waste etc.). This is because the organic components can be recycled. For example, plans will release their nutrients into the soil as they decompose. You can have a detailed look at this process in our article Nutrient Cycles.

Biofuel can be defined as any fuel that is derived from biomass.

We use many types of biomass fuel in our daily lives. Wood is the biggest resource.

Fig. 2 - Biomass sources in an ecosystem

### Forestry residue

Trees removed for commercial use usually leave unwanted parts in the logging sites. Pre-commercial thinning is often performed. The biomass used for fuel will include dead trees, commercially "unfit" trees (from thinning) and other unwanted parts such as diseased branches.

Pre-commercial thinning removes some trees to give others enough space to grow.

Scotland has 1,318,000 hectares of woodland, which generates sustainable fuel for around 250,000 houses! Maybe your house is also fueled by the Scottish forest if you live in Scotland.

A lot of this waste will also be used by the industry making the waste.

### Dedicated energy crops

Crops may be grown not only for food but also to provide biomass for fuel. There are two types of dedicated energy crops - herbaceous and woody.

Herbaceous crops, such as wheatgrass, are perennial, which means the plants will usually live for more than three years. Wheatgrass has high biomass and is classified as a C4 plant.

C4 plants contain the enzyme PEP carboxylase, used in 'carbon fixation'. This process assimilates carbon compounds into more usable forms for the plant.

C4 plants are more efficient than C3 plants (which use the enzyme RUBSICO) due to their high rate of photosynthesis and reduced photorespiration. Photorespiration is a wasteful pathway where the enzyme RUBISCO (in C3 plants) will use oxygen rather than carbon dioxide.

Woody plants include fast-growing hardwood trees (dicot trees). For example, maple, cottonwood and walnut trees.

### Agricultural crop residue and animal waste

Agricultural crop residue often includes wheat, rice straw and corn stover. The residue is usually used to produce animal feed. Crop residue can also minimize soil erosion by wind and water. It can also provide thermal protection to the plants during cold temperatures.

Animal waste is often used as a natural fertiliser in agriculture. Livestock manure can also be used to produce fuel. The fuel can generate electricity for industrial and domestic heating and transportation.

### Municipal waste and sewage

Municipal solid waste and commercial waste can be used to make refuse-derived fuel. Food waste collected with your recycling will also be biofuel. Alternatively, you could make your own compost from your food waste if you have a garden.

First, sewage will be treated to produce sewage sludge. After the treatment, it can be used as a fertiliser by the farmers. The leftover water containing invisible dirt particles will undergo other treatments to remove harmful bacteria.

## Advantages and disadvantages of using biomass within the renewable fuel industry

We will cover some advantages and disadvantages of using biomass as a fuel resource.

 Advantage Disadvantages Renewable energy source Although renewable, it is not completely clean (it will still produce air pollutants but less than non-renewable fuel) Carbon neutral Higher cost compared to other renewable alternatives Less dependency on burning fossil fuels Possible deforestation Reduces waste Biomass plants will require lots of space Less expensive than fossil fuels Biomass is not as efficient as fossil fuels

Table 1. Advantages and disadvantages of biomass as a renewable fuel source.

Although biomass has a lot of advantages and the potential to be a good renewable source, it is still in its early developmental stages compared to other renewable sources, such as wind and solar power.

Biomass used as fuel is largely held back by its lower efficiency, space and costs. Biofuels are often blended with conventional fuels to counteract this efficiency problem and improve fuel economy. However, the efficiency still needs to be tackled before biomass can be a completely viable alternative to fossil fuel.

## Biological farming

Biological farming can be defined as a chemical-free method of farming practices. Biological farming focuses on improving the microbiology of the soil to increase plant growth and produce yield.

### Practices to increase the efficiency in energy transfer

To increase efficiency, farmers could:

• Reduce respiratory losses of farmed animals, such as reducing their movement. More energy will be transferred to the human food chain.
• Simplify human food chains. This will also lead to higher efficiency as less energy is lost to weeds and pests. You can do this through the use of herbicides and insecticides.

### Advantages of biological farming in agriculture

We will discuss the main advantages of biological farming practices.

#### Sustainability

Biological farming aims to establish long-term soil fertility without artificial fertilisers, which require non-renewable resources for production. Organic fertilisers are used instead, such as manure and compost.

Biological farming allows the soil to sequester carbon. Various management practices such as integrating nitrogen-fixing legumes and crop rotations can increase carbon return into the soil. This helps to mitigate the greenhouse effect.

The greenhouse effect is a process that warms the Earth's surface.

You have most definitely heard about global warming mentioned before. This is for a good reason! Most of what you may have heard is about raising awareness on this issue because we are the main cause. By burning fossil fuels, there has been an increase in greenhouse gasses, i.e. gasses that trap heat in our atmosphere. This includes carbon dioxide and others such as nitrous oxide.

The heat trapped in the atmosphere raises our Earth's temperature, affecting not only us but species diversity. In the areas where the temperatures have risen more than a species can tolerate, consequences such as suitable habitat loss and even death follow. A good example is bleaching in the coral reefs due to temperature rises.

#### Biodiversity

• At the gene level - organic farms use traditional and adapted seeds. These are better adapted to battle diseases and more resilient to other external factors (e.g. climatic stress).
• At the species level - organic farms can act as refugee locations for wild plants, preventingbiodiversity loss in the area.
• At the ecosystem level - as an overall view, the ecosystem in an organic farm will generally produce a lower yield of crops. However, it will have greater biodiversity of species.

#### Oil

By growing a diverse combination of plants and animals, soil content is improved, and the nutrients and energy are recycled. More structured soil will reduce erosion and provide shelter for soil-living organisms. You will attract re-colonizing species, including birds, pollinators, and pest predators, by not using pesticides.

There are disadvantages to organic farming as well. Some examples include:

• Organic farming will often produce a lower yield.
• The quality of the crop will fluctuate during different years and seasons.
• Higher costs of the product.
• More intensive work is required, and more monitoring is required.

## Biomass - Key takeaways

• Biomass can be defined as the total organic matter in a given area or volume at a given time. Biomass is an important source of renewable energy.
• Biomass within the ecosystem can be hard to measure due to varying amounts of water within the living organisms. Often food biomass pyramids can visualize the movement of energy through different trophic levels.
• The types of biomass used in the renewable fuel industry include crop residue, wood, municipal waste and others. Biomass as an energy source still requires development, and there are advantages and disadvantages to the practice.
• Biological farming is a chemical-free way to grow crops and animals. It improves the biodiversity of plants and animals in an ecosystem.

#### Flashcards in Biomass 15

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What is biomass?

Biomass can be defined as the total organic matter in a given area or volume of the aquatic and terrestrial systems at a given time.

Is biomass renewable?

Biomass is renewable because it is derived from renewable sources such as manure.

What are the advantages of biomass?

1. Biomass is renewable and carbon neutral.
2. Biomass has a lower dependency on burning of fossil fuels. It will therefore reduce waste.
3. Using biomass as an energy source is less expensive than using fossil fuel.

How does biomass energy work?

Biomass is primarily produced by the producers through photosynthesis. Biomass can be burned to produce energy or converted to gaseous or liquid fuel.

What are five types of biomass?

1. Crop residue
2. Animal waste
3. Wood and wood chips
4. Municipal sewage
5. Industrial waste

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