Biomass energy is the energy that is produced from the transformation of organic matter. There are two ways in which this energy can be obtained: either through combustion of biomass or its transformation into biofuel. This latter process is more complicated and implies different methods of doing so. Biomass plants can use chemical, thermal, or biochemical reactions to obtain biofuels.

Image source: pixabay.com

Over the course of this article, we will be talking about these three processes involved in the creation of biofuel from biomass, as well as about combusting biomass directly into energy. We will also explain how the three reactions (thermal, chemical, or biochemical) fall into play in the grand scheme of biomass. Before that, however, we must make sure we understand the gist of things, i.e. three questions:

• What is biomass? What are the sources that can be used to produce biomass? Which of these yield the most energy and that are considered best for the environment?
• How is biomass transferred to energy? What is biomass combustion and what are biofuels?
• What are the methods of transforming biomass into biofuels? Which is the safest for humans and the environment?

What Is Biomass?

To give a plain and simple biomass definition, it is a matter obtained from living organisms, or from organisms that have recently deceased. This does not necessarily mean dead animals, as some may think. More often than not, the term “biomass” is used to refer to lignocellulosic biomass. So, when people ask ‘what is biomass?’, they’re actually asking what lignocellulosic biomass is.

Lignocellulosic biomass is made from the dry matter of plants. As a few readers may already know, this naturally occurring resource is extremely common. Thus, it’s perfect for the creation of biofuels since making biomass energy from dead plants is not only cost-efficient but also extremely good for the environment (in more ways than one). Still, nitpicker critics of biomass energy have managed to find some interesting problems with it. We’ll talk about this in the latter part of this article.

For now, it’s important to know that while the majority of biomass is of the lignocellulosic, not all of it comes from dead plants. Below you can see a diagram of the resources that are often used in the creation of biomass energy.

Image source: wiredcosmos.com

What Is Biomass Energy?

Biomass energy is what results after the combustion or transformation of biomass. The energy output depends equally on the process used for transformation, as well as on the exact type of biomass used. Because of this, one cannot exhaustively define biomass energy, but rather the different types of biomass energy such as plant energy and waste energy.

What Are the Sources of Biomass?

Now that we’ve covered the definition of biomass energy, it’s time to look at its exact sources. Believe it or not, the discovery of biomass energy by humans dates back to the very first campfires made by primordial humans in times immemorial. The wood people burn to make a fire actually represents the first resource humans used for biomass. Naturally, this also means it’s the most common resource today. Let’s see a list of all the prime matter types:

• Wood: dead trees, stray branches, stumps, chips, and clippings;
• Plants: straw, corn, sugarcane, wheat;
• Garbage: municipal solid waste, waste from manufacturing plants.
• Waste: human waste, animal waste, rotting garbage.

Plants are great as biomass since they can be harvested with relatively low energy consumption, offering a high yield per hectare. Corn, sugarcane, wheat, and other grains are favorites for the production of biofuels such as bioethanol. Straw, on the other hand, is much more practical when used as a combustion fuel to produce both heat and electricity.

Two types of garbage or waste energy from solid residue can also be produced from biomass. Using municipal solid waste (garbage) from landfills and residue from various manufacturing plants, biomass factories gather two types of resources. First, they create heat and electricity through combustion (burning garbage). Secondly, they use the biomass gasses that these wastes produce to combustible fuels (ethanol, methanol, or methane).

Human waste, animal waste, and decomposing garbage can all three be used as biomass. The main use is the production of combustible fuels. Another important way to achieve green biomass energy is by using leftover cooking (vegetable) oil and animal fat. The biodiesel fuel that results from this process can produce as much as 90% of the energy that traditional diesel fuel makes. This type of fuel not only presents a reasonable alternative that is cheaper for the consumer but is also a way in which the world can turn down on its wasteful petrol-dependent habits.

Image source: energy.ca.gov

Transforming Biomass into Energy

Besides the obvious processes of combustion and/or decomposition (pictured in the image above), biomass can be converted into energy via the process called biomass transformation. As we’ve already stated at the beginning of the article, there are three methods of doing this: through chemical, thermal, and biochemical reactions.

The three procedures mentioned above are used to create biofuels. Before we go on to understand these exact reactions, we need an ample and simple definition of what a biofuel is.

What Is Biofuel?

A biofuel represents the fuel that is obtained via biological processes either in controlled laboratory conditions or in biomass plants. Biomass plants usually produce renewable biofuels through a process known as contemporary carbon fixation. Unlike natural carbon fixation, which involves thousands, possibly millennia (think of the creation of coal), today’s methods speed up the biological process.

Unlike fossil fuels, which release the carbon back into the atmosphere, most biofuels are completely eco-friendly and do not increase the carbon emissions. An important fact to note is that not all biofuels have zero emissions. The biofuels created as biomass energy are of two types, depending on what types of biomass were used:

• First generation biofuels. Using biomass sources such as corn starch, or sugarcane residues, first generation biofuels are created as a result of the fermentation of the sugar in these residues. The resulting fuels are alcohol based and can be used to make electricity directly or can be added to gasoline. An example of first generation biofuel: biodiesel, bioethanol.
• Second generation biofuels. With biomass featuring mainly agriculture residues and municipal wastes, the process to create second generation biofuels is trickier. Lignocellulosic biomass ingredients are common in the creation of this type of biomass energy. The sugar monomers of the polymers in plant dry matter is used to create fuels such as bioethanol (again).

Although the second generation of biofuels is largely preferred to the first, its fuels are also very difficult to create. This is not necessarily because of the lack of research in the field of biochemistry, as because of the unstable technology that has not yet figured workarounds to counter the structural rigidity or the chemical inertness of the lignocellulosic biomass.

Image source: cleantechnica.com

Biomass Energy Conversion Processes

Although we have mentioned only the three main ways of transforming biomass into biofuel, there are in fact four of them. In the following part of this article on biomass energy, we will be taking a closer look at these. The image above is a very good example of the process implied when you hear the words ‘thermal biomass conversion.’ Incidentally, we will start with this one:

Thermal Conversion of Biomass Energy

This process uses thermal reactions to heat up and obtain energy from almost all types of biomass mentioned above. The methods involved transform the biomass into other useful chemicals. Depending on the chemical reactions involved and the temperature at which the energy is created, there are four types of thermal conversion:

• Biomass thermal conversion through combustion;
• Biomass thermal conversion through torrefaction;
• Biomass thermal conversion through pyrolysis;
• Biomass thermal conversion through gasification.

While the meaning of combustion may be obvious, definitions for the other three may be required.

What Is Torrefaction?

The torrefaction of biomass is a process by which bio-coal can be created. The reaction happens at temperatures ranging from 200 to 320 degrees Celsius. Torrefaction removes any trace of moisture and volatiles from the biomass, leaving behind something that is essentially coal, but looks more like a briquette or a pellet. Besides advantages in logistics (transporting briquettes is much easier than transporting coal), biomass that undergoes torrefaction is also good for the environment.

What is Pyrolysis?

Pyrolysis represents the thermochemical decomposition of biomass. Through this process (which is only made in the total absence of oxygen and halogen), biomass is converted into bio-coal and other useful materials. A good example of pyrolysis is when volcanoes erupt and cover plant life in lava. The temperatures involved (200-300 degrees Celsius) are precisely the ones needed for pyrolysis. This method is also used to turn plastics into reusable oils.

What is Gasification?

The most advanced process of the four involved implies the heating of biomass at extremely high temperatures (over 700 degrees Celsius) without lighting it on fire. Controlled steam and oxygen are released during the reaction. The final results of the method are carbon monoxide, carbon dioxide, and hydrogen. The compound gas made up of the three is called a syngas. Syngas is a biofuel that is extremely flammable, and its combustion is a great source of energy, as well as a good alternative to fossil fuels.

Chemical Conversion of Biomass Energy

Converting biomass into sustainable, eco, and renewable biofuel is often an expensive process. The chemical method is by far the most expensive. It involves, first of all, the gasification of the biomass. Given the highly dangerous conditions in which biomass can be gasified, it’s a high-risk job, and the costs are usually very high. Part of the problem is that biomass can’t be introduced into a stable pressure chamber at such a high temperatures as easily as coal or other elements can.

However, the greatest advantage of chemical conversion is that it can make absolutely any type of biomass into biofuel through the process of gasification. Also, there are two ways in which biomass energy can be created through chemical reactions:

• Selective conversion. This process involves creating specific chemical elements through a sort of reverse engineering at the chemical level. Through this, chemists can break down biomass into intermediate chemicals such as glucose or sorbitol, which can be then converted to hydrocarbon fuels.
• Basically, the method by which biodiesel is created from biomass. If we’re to look at the more complicated definition of this process, transesterification implies converting one type of alcohol and one type of ester into another type of alcohol with another type of ester.

Biochemical Conversion of Biomass Energy

This process of transforming biomass energy into biofuels via biochemical conversion is as close to real life biology as you can get. Biochemical processes are a big hit among those seeking to make renewable biofuel out of biomass. In nature, there are different ways in which biomass is decomposed. Biochemistry has sought to mimic these ways in laboratory controlled experiments.

One ingenious way in which biochemical conversion does this is by using microorganisms and bacteria usually found decomposing the same type of biomass in nature. The organic matter is digested, decomposed, and transformed into compost.

Electrochemical Conversion of Biomass Energy

A simpler but far less popular process of transforming biomass into biofuel is electrochemical conversion. What does this imply? The converting of biomass into electricity directly through the process known as oxidation. Through electrochemical conversion, carbon, ethanol, or microbial fuel cells can be created.

Image source: alternative-energy-news.info

The Biomass Pyramid

We’ve tackled the definition of biomass. We’ve talked about what goes into biomass energy and what comes out of biomass energy. We’ve even seen what the exact procedures by which biomass energy is created are. While doing this, we’ve also shown how great an alternative fuel biomass can produce. The image above, for instance, shows the exact process that transforms oil crops (such as sunflower crops) into biodiesel. Now, we’re going to look at a more interesting generalization: the biomass pyramid.

What Is the Biomass Pyramid?

A biomass pyramid is a representation of the producers and consumers within a specific ecosystem. The structure of the pyramid is chosen especially so that the width of each level adequately represents the population of the respective category.

The structure of the biomass pyramid contains the following levels:

• A producer level. This level is usually occupied by biomass. Biomass is created naturally and thus does not need to consume other levels to exist. This level is also the most populous.
• A primary consumer level. The second level of the pyramid also encompasses a large population. This one represents the primary consumers – usually those microbes and small life forms that feed off of the biomass.
• A secondary consumer level. The third level of the pyramid isn’t as large as the other two. Small animals begin to appear here and even the first predators.
• A tertiary consumer level. This is usually the top of the pyramid (unless the consumers are further divided into separate levels). The top predators of the ecosystem sit on this level. For a marine ecosystem, this level would probably be occupied by the hunters: sharks, octopuses, or whales.

Despite its suggestive name, the biomass pyramid isn’t connected to biomass energy in too many ways. Most importantly, biochemists usually look at the biomass pyramid of the area where the biomass they’re using has come from. They do this so as to find the primary consumer level so as to harvest them and transform their biomass into compost. Here’s a relevant illustration of a typical biomass pyramid:

Image source: earth.rice.edu

Advantages and Disadvantages of Biomass Energy

Although there are mostly advantages to using biomass energy, the critics of this type of eco-friendly, self-sustainable means of protecting the environment do bring some good arguments. We’ve compiled a small list of the pros and cons of biomass energy: