It's becoming increasingly recognized that the world will never run on 100% renewable energy unless cheaper batteries are produced. Even then, the use of batteries creates a whole new set of issues to contend with, mainly their environmental impact and further need for safe and sustainable disposal after their use.
Bioenergy remains a crucial component of renewable energy generation throughout the globe. It currently constitutes 60% of renewable energy produced in Europe and is set to retain its position as a main player in the changing energy scene as the world aims to become carbon neutral. However, bioenergy is only beneficial if managed sustainably.
Bioenergy contributed 39% to renewable energy generation in Ireland in 2017.
There are three main forms of bio-energy that exist in mainstream conversation concerning renewable energy generation. These are biofuels, biomass and biogas. They are explained in more detail below.
Biomass is organic material such as wood that can be combusted to produce heat energy or electricity.
Electricity is produced through steam generation which turns a turbine, similar to a fossil fuel power generation plant.
Biogas is a gas primarily composed of methane that is produced through the decay of animal waste and other matter.
Considered as a potential replacement to natural gas.
3. Liquid Biofuels
Fuels derived from organic matter which can be used in place of traditional gasoline fuels.
Three known generations, each with difficulties which have hindered use worldwide.
The Carbon Budget
This of course varied at times due to certain global events but the end result has always been that the earth would always have a manageable amount of carbon dioxide in its atmosphere, changing naturally throughout its history in a controllable manner.
Decaying organic matter and respiration would release carbon dioxide into the atmosphere, which would then be used in the growth of plants thereby effectively cancelling out any excess carbon dioxide in the atmosphere.
In order to understand the proposed benefits of bioenergy over fossil fuels, you will need an understanding of the carbon budget of the planet. From the beginning of photosynthesis on earth, the release and sequestration of carbon dioxide has existed in balance.
When humans started burning fossil fuels and cutting down trees we upset this balance. Now carbon dioxide which has been stored underground over millions of years has been released into the atmosphere through the burning of fossil fuels. On top of this, widespread deforestation has meant that it's impossible for plant growth to abate this new source of carbon dioxide. As a result, the earth has too much carbon dioxide which is quickly warming the planet. In order to prevent global warming we will need to restore this carbon balance. The burning of fossil fuels will always disrupt this balance, no matter how clean the process.
Based on this it would appear safe to label bioenergy as a green, renewable source of energy. This is what many governments worldwide do, with most renewable energy generation statistics consisting significantly of bioenergy sources, mainly biomass. Unfortunately bioenergy, especially biomass, is not as renewable as many would have us believe.
In most recent findings, bioenergy accounts for 12.4% of final global energy consumption whereas it contributes to 50% of all renewable energy generation.
Biomass constitutes a large proportion of this. Biomass can be used to generate electricity in biomass plants and to produce heat in the form of wood pellet burners or traditional stoves.
Biomass contributes around 95% to renewable heat generated.
Where it comes from
Biomass relies heavily on the forestry industry, with approximately 87% of fuel sourced from forestry. Wood is used to burn in solid fuel stoves and in the production of wood pellets.
The rest is accounted for by charcoal and similar substances.
Why Biomass isn't Renewable
There have been many concerns about the actual benefits of biomass with regards to reducing CO2 emissions. It is often touted as a carbon neutral form of energy but this in almost never the case. In reality, CO2 is produced throughout the entire process of biomass production and consumption.
The soil is a natural carbon sink. It's being realized in recent years that when old growth forest or grasslands are cleared for a biomass plantation, large quantities of CO2 is released. In Ireland, peatlands store a huge quantity of CO2. The alteration of peatlands to make way for forestry releases vast amounts of carbon stored within the ground. It is incredibly difficult for the new biomass plantation to abate this released carbon. Old growth forests also capture more CO2 than younger equivalents and so the destruction of forests for biomass plantations is counter intuitive.
It would also take decades before the consumed biomass is abated through new forestry plantations. Global warming requires urgent action. The use of biomass will result in a large influx of short term CO2 emissions which will contribute greatly to the warming of the planet. By the time these emissions are removed by new growth forests it may be too late.
Most biomass plantations are also a mono-culture of one tree species, which is not beneficial to the overall health of the ecosystem. Mono-culture forests are planted solely for commercial gain and do not support healthy populations of plants and animals.
Transportation of biomass from the area of harvest to a biomass plant produces a lot of CO2 emissions. This is worsened where biomass is actually imported from overseas which is a significant contribution to transport emissions. The European Union is one of the largest consumers of wood pellets worldwide and also one of the largest importers of wood pellets. It is expected to import 12.1 million tonnes of wood pellets while producing 18.1 million tonnes in 2019, equating to 40% of wood pellets used in Europe coming from overseas. A large quantity of these come from the United States.
The UK was the top consumer of wood pellets in 2018, consuming 8 million metric tonnes, while importing 7.829 million tonnes of this, a staggering 98%.
Biomass is not used as extensively in Ireland in comparison to other countries in Europe. Despite this, it still contributed 27% to renewable energy generation in 2017, with this figure projected to increase. Unfortunately biomass contributes 79% to renewable heat generated in Ireland. Biomass is the second largest source of renewable energy in Ireland after wind power. This could continue to grow in order to meet targets unless action is taken to declassify it as a renewable energy source.
Biomass could have the potential to be a less carbon intensive source of power if certain conditions are met.
1. Wood material sourced from local forests located close to processing plants, eliminating overseas imports and reducing emissions from transport.
2. Forests managed in a sustainable way - forests quickly replaced.
3. Plantation of forests solely for biomass production does not replace old growth forests or result in a large disruption to carbon sequestering habitats, e.g. peatlands.
Unless all of these conditions are realized, along with a transparent and accountable production cycle, biomass will never be a renewable source of heat and electricity.
As long as there is a market for biomass world-wide, there will be a portion of it produced unsustainably. Governments are using biomass to bolster up their renewable energy generation statistics, which will only result in long term damaging effects to the planet.
The EU has pledged to only source biomass from sustainable sources, but it is unlikely that they will ever be able to meet these requirements. Countries continue to turn a blind eye to the damaging effects of biomass, instead favouring short term statistical gains.
As mentioned, reliable non-intermittent source of energy will have to be used to supplement renewable energy. Many people have suggested using natural gas to fill this gap, which is the cleanest of the fossil fuels. This still involves the burning of fossil fuels however and can only be considered a short term solution to renewable energy intermittency.
Another proposed form of energy is biogas, which is gas derived from decaying organic feedstocks under anaerobic (no oxygen) conditions. This gas is composed of methane and CO2. Methane is also the primary component of natural gas and so biogas is a realistic substitute to natural gas.
Biogas can either be burned in a boiler, used in a CHP (combined heat and power) plant or upgraded to pure biomethane through the removal of CO2.
1. Landfill waste
2. Animal slurries
3. Grown crops i.e. silage
Biogas is considered a renewable fuel as it uses carbon which is essentially part of the earth's carbon budget and is not adding any new carbon dioxide to the atmosphere. As long as no fossil fuels are used in its production then it can be considered renewable, although this will be difficult. Biogas will always be produced from decaying organic matter on farms and landfills. Farming in particular is going to have to adapt in order to reduce their emissions, as it is a major emitter in Ireland and throughout the globe. Implementation of biogas as a renewable energy source is one potential way of doing this.
The video to the right details the operation of a large biogas plant in Denmark.
Biogas in Ireland
Energy contribution in Ireland?
Biogas produces approximately 3% of renewable heat in Ireland and an insignificant amount of renewable electricity. It is still a relatively new and underdeveloped technology in Ireland.
In 2017 28 GWh of electricity was produced using sewage sludge gas collected at waste-water treatment plants.
14 GWh was produced from biogas CHP in industry (animal slurries, brewery waste, other agri-food sector wastes).
Current Biogas plants in Ireland
There are currently around 30 biogas plants in Ireland, with 10 using animal by-products. This is very small in comparison to other countries such as Italy and Germany with a total of 1900 and 9000 anaerobic digesters respectively.
Potential for Biogas in Ireland
Biogas could provide energy equivalent to approximately 30% of our current natural gas supply.
This would go a long way in reducing future dependence on non-intermittent fossil fuels.
Biogas and Agriculture
The wide-scale implementation of a biogas industry in Ireland will be a considerable challenge. The conversation surrounding the potential of biogas in Ireland is usually centered around agricultural waste. This presents a large problem in itself as agriculture in Ireland consists of a large amount of small, potentially isolated farms.
Transport of animal waste from each smaller farm to a suitable anaerobic digester would be essential, which creates new problems with regards to transport emissions. A large investment would be required in order to create and successfully support a biogas industry.
It is unlikely that individual farms would invest in their own biogas digesters. A lot of Irish farms are too small to warrant the installation. A countrywide network of evenly distributed digesters is thought to be more appropriate.
Grass silage would be a significant contributor to biogas in Ireland, much higher than that of animal waste. This creates issues however with the potential of growing silage just for the biogas industry, which could result in conflicts with livestock farming and the forestry sector.
Despite this, agriculturally sourced biogas could be a great way for farms to offset some of their carbon emissions while also serving as a source of additional income for many farmers.
3. Liquid Biofuels
Liquid biofuels are fuels produced from biomass which can be used in the place of fossil fuels to power our modes of transportation. The two most common types of biofuels are ethanol and biodiesel.
Biofuels have been long encouraged as a green replacement to fossil fuels but there have been a number of notable issues throughout their history.
How are biofuels made?
There are many different types of biofuels and so there are many known methods to produce them. Liquid biofuels are generally categorized into one of three categories, known as generations. Looking at each of these generation in detail is the best way to see the production of each type of fuel, while also getting an insight into the various problems biofuels pose.
Feed-stock: Derived from crops such as corn, sugarcane, soybeans and vegetable oils such as palm oil.
Method of production: The sugar, starch or vegetable oils found within these crops is converted into bioethanol or biodiesel by a process known as transesterification or by yeast fermentation.
Biodiesel is produced by extracting oil from plants or seeds and can be used as a diesel substitute in diesel engines.
Problems with first generation biofuels: First generation biofuels are unfortunately not a green source of energy and their production is resulting in an increase in carbon emissions. These biofuels are produced from food crops which must be grown on arable land. The issue with this is that vast swathes of forest worldwide, primarily the Amazon Rainforest, have been cleared in order to make way for the growth of biofuel crops. Rainforests and other forests worldwide are crucial carbon sinks and their destruction contributes heavily to global warming.
The desire for crops such as corn for the use as biofuels has also driven up the cost of certain food crops, which in turn is starving poorer populations which use these crops as a staple food source. This is known as the food vs fuel debate and is a major disadvantage of first generation biofuels.
Despite this many countries, especially the USA, continue to use and promote first generation biofuels as a green energy source. The United States views biofuels as an attractive option to help support many struggling farmers in the country. There are schemes in place ensuring that biofuels are required in certain gasoline mixes, with large incentives given for energy crop growth. Many politicians promise support for the biofuel industry, securing votes from the agricultural community in the process. For this reason, it is an incredibly difficult issue for many politicians in the USA to handle, and it does not appear that support for biofuels will wane anytime soon.
Feed-stock: In an attempt to solve the fuel vs fuel debate, second generation biofuels are sourced from residual non-food parts of currently grown crops, non-food crops such as miscanthus and switchgrass and also industry waste such as forestry waste and woodchips. All this biomass is composed of woody or fibrous material, which are cellulosic in nature.
Method of production: Various methods required to extract the sugars and oils from the wood-based material such as pyrolysis, gasification and hydrothermal liquefaction.
Problems with second generation biofuels: While second generation biofuels are not made from food crops, issues still persist with carbon emissions.
Residues which were normally left to become part of the soil are now collected and processed. These residues are a natural fertilizer and bind more carbon to the soil, and so removing them actually results in a decrease in soil quality and an increase in CO2 emissions.
Fertilizer and pesticides are also often required which contributes to total carbon emissions of the process while also having a negative impact on animal and plant life.
Despite this, it is believed that under conditions promoting sustainability and directly attempting to minimize carbon emissions during the production cycle, second generation biofuels can in fact result in a decrease in carbon emissions. It's unknown if that decrease is substantial enough for them to be considered a 'clean' energy source.
Currently it is still quite difficult to efficiently extract the necessary sugars and oils from the non-food crops which makes second generation biofuels an unattractive option from an economic perspective. However, advancements are being made and the global market for second generation biofeuls is expected to grow.
Feed-stock: Third generation biofuels were created in efforts to bypass the difficulties associated with extracting usable substances from cellulosic materials. The feedstock is algae.
Method of production: Algae is oil rich and this can be extracted and turned into usable biofuels. The remaining plant matter can be converted into ethanol or similar fuels.
The algae can be grown in open ponds or closed loop systems.
Algae are an attractive biofuel option due to their high lipid content and high growth rate.
Problems with third generation biofuels: Similar problems plague the widespread implementation of third generation biofuels as first and second generations.
The actual production of fuels from the algae is a difficult and carbon intensive process. Algae farms require a huge amount of water, CO2 and fertilizer to allow the algae to grow quick enough for large scale production. It is also difficult to continuously maintain suitable growing conditions in open ponds.
The extraction of lipids from the algae which is used in biodiesel is not very efficient and is the main limiting factor in their use as biofuels. Until this is solved third generation biofuels will never be considered a viable fuel source.
Liquid Biofuels in Ireland
99% of renewable transport in Ireland is sourced from liquid biofuels, with 81% from biodiesel and 18% from biogasoline. Liquid biofuels contributed 13% to renewable energy sources in Ireland in 2017.
It is difficult to find much information on liquid biofuels produced in Ireland as we rely on imports. It appears that most of our biodiesel produced comes from tallow, oilseeds and recovered vegetable oil.
Biofuels are of most interest to the agricultural industry as biofuels could be a new reliable source of income for farmers.
This scheme was introduced in 2010 in order to meet Ireland's commitments under the EU Renewable Energy Directive 2020, which is a target of 10% renewable energy in the transport sector by 2020.
Under this obligation, road fuel suppliers must include a minimum percentage of renewable fuels in their fuel mix sold to consumers.
The rate is currently 8.695% but as we have seen it's reasonable to question the environmental benefits of this scheme as there is not enough clarity on the benefits of biofuels, particularly in Ireland.
Biofuel Obligation Scheme
Fast growing crops such as willow and miscanthus have potential in Ireland but currently the market is not profitable to warrant farmers investing in the industry. The majority of biofuels used in Ireland are imported which led to the closure of several indigenous biofuel production plants in in the country.
The biofuel industry in Ireland is currently at a stalemate. It is accepted that the biofuel industry in Ireland will never take off unless there is an increase in market prices for energy crops. It's also inevitable that land currently used for forestry or livestock would be used for biofuels, which will ignite the food vs fuel debate in Ireland. Given the current skepticism about the environmental benefit of biofuels, perhaps it is better if the industry remains where it is.