One of the oldest life forms, algae, holds the highest potential for future energy generation. This third generation (3G) biofuel holds some major advantages over other biomass but it has not yet taken off as once expected. With increased focus and attention, innovative techniques in research and development, and political will, algae can return to the fore-front of future biofuel production.
Higher biofuels yields are a major advantage of algae over first generation (1G) plant crops such as sugar beet or wheat, and second generation (2G) sources for biofuels such as vegetable or animal waste streams. Estimates provided by Rocca et al (2015) in table 1 below indicate the stark differences in estimated oil yield potential per unit area for different terrestrial crops and microalgae. Microalgae also have rapid growth potential and can double their biomass in as short as 3.5 hours, and are capable of year-round grow (Cheng, 2018).
There is a diverse range of biofuels that can be derived from algae. Biomethane, bioethanol and biobutanol can be derived from macroalgae or seaweeds. Biodiesel, biomethane, bioethanol, bio-oil and bio-hydrogen can be derived from microalgae (Rocca, et al., 2015). Microalgae species are favourable for fuel production due to high lipid contents of 50 – 70 % (Khan, et al., 2018). Algae cultivation can be done in open systems such as ponds and lakes, and in more advanced closed-loop systems on land unsuitable for food crops, removing the concern of competition with food producers. Closed-loop systems offer the added advantage of additional control over variables such as light, temperature, nutrients, pH, and the particular species grown, to enable producers to maximize crop production. Algal growth can be combined with wastewater treatment systems to recycle waste nutrients such as nitrogen and phosphorous to help mitigate greenhouse gas emissions and protect our environment. Microalgae also produce valuable coproducts such as proteins and pigments, and the left-over biomass after oil extraction can be used as feed, fertilizer, or fermented to produce methane or ethanol (Cheng, 2018).
With so many advantages it is clear that algae have been held back from their high expectations as no commercial algae-based biofuel currently exists. It can often require more energy to remove moisture from algal biomass to enable lipid separation, than the energy the end product provides. This has long been a point of friction and research continues into a much-needed energy-intensive drying process that would enable algal biofuels to compete for market share. The high operational, maintenance, harvesting and conversion costs, have meant that it has not yet become feasible as a biofuel (Khan, et al., 2018). Rising CO2 prices as a result ofstringent CO2 stabilizing techniques make the economics of microalgal biofuel unattractive, and production and combustion of microalgal diesel releases as much CO2 as is captured from anthropogenic sources and assimilated by microalgae (Takeshita, 2011). There is at present no comprehensive analysis on the deployment potential of optimized harvesting methods at large scale, from the point of view of technical viability, environmental impacts and cost effectiveness (Rocca, et al., 2015). Environmental and social concerns raised by the production of biofuels from algae include the high demands on key resources such as energy, nutrients, water and CO2’ along with the availability of land with suitable characteristics including climatic conditions and an adequate supply of resources (Rocca, et al., 2015).
There is no doubt there are major challenges to be overcome before biofuels from algae are a viable alternative. The potential is there however and with focus on energy efficient and low-cost harvesting and dewatering techniques, there is a positive future ahead for algae biofuel production.
Cheng, J., 2018. Biomass to Renewable Energy Processes. 2 ed. s.l.:CRC Press.
Khan, M., Shin, J. & Kim, J., 2018. The promising future of microalgae: current status challenges, and optimization of a suatainable and renewable industry for biofuels, feed, and other products. Microbal Cell Factories, 16(36).
Rocca, S., Agostini, A., Giuntoli, J. & Marelli, L., 2015. Biofuels from algae: technology options, energy balance and GHG emissions, s.l.: European Union.
Takeshita, T., 2011. Competitiveness, role, and impact of microalgal biodiesel ain the global energy future. Applied Energy, 88(10), pp. 3481 – 3491.
Biofuels produced from renewable energy sources have become a hot topic in the pursuit of finding a replacement for fossil fuels. This is motived due to the high dependency of fossil fuels in the transportation sector, which releases large amounts of greenhouse gases. After many years of attempts and research, progression can finally be seen and actual energy efficient biofuel options are out on the market. There still an ongoing discussion of which biomass is the most suitable to produce biofuels from and from there biofuels have been divided into four different generation. The generation of biofuel is based on the composition or origin of the biomass it is produced from, to simplify, take a look at the figure below.
Figure 1. Different generations of biofuels (Ertem, Kappler, Neubauer, & Acheampong, 2016).
However, a biofuel produced from a renewable energy source does not automatically equal to an sustainable alternative. In fact, there are some down sides to them as well. First generation biofuels are cheap but have received some criticism, where the sustainability of it have been questioned. Besides repurposing arable land for fuel instead of food production, producing ethanol from sugar canes or maize is not effective enough and the process can in some cases require more energy than it generates (Olaganathan, Lee, Tong, Cheston, & Yi, 2014). Looking into other renewable resources, the energy efficiency increases. Since I live in Sweden, the first biomass that comes to mind is wood, an energy source with high availability. Wood, and plants in general, are considered lignocellulosic materials consisting of lignin and polysaccharides cellulose, hemicellulose (Zafar, 2020). Lignocellulosic materials are considered biomass for second generation (2G) biofuels, since it is produced from non-edible plants. Being able to use wood scraps (and even agricultural waste) is one of the advantages of lignocellulosic materials, creating a more circular process for e.g. the forest industry. Other advantages include these plants not needing as much fertilizer, not exhausting the soil they grow in as much and can be grown on marginal land. Besides growing trees not compromising food security, they can be grown in a carbon neutral way, meaning that the carbon being released when burned is captured when new trees are being planted. Furthermore, depending on where in the world production occurs the type of wood may vary. In China and South America it is more common to use fast growing trees (Potters, Goethem, & Schutte, 2010).
The process scheme of turning lignocellulosic biomass into ethanol is summarized in Figure 2. First, the polysaccharides needs to be hydrolyzed and broken down into simple sugars (saccharides), this is done by adding enzymes or acid. The following step differ from different producers, but in general microbes are added in order to ferment the sugars into ethanol. Finally, this ethanol is purified through distillation and the ready to be prepared for distribution (Zafar, 2020).
Figure 2. The production process of producing bioethanol from lignocellulosic materials.
2G biofuels are more sustainable, but one of its biggest drawbacks is its limited possibility of commercial upscaling (Olaganathan et al., 2014). Since the resources exist it is of great importance that the governments and politicians take action and start to see the benefits of using lignocellulosic biomass instead of food for fuel production purposes. Hopefully, with the need for new technologies and fight towards climate change, the 2G bio fuel industry will have a leading position in the race of replacing fossil fuels.
Ertem, F. C., Kappler, B., Neubauer, P., & Acheampong, M. (2016). In pursuit of Sustainable Development Goal (SDG) number 7: Will biofuels be reliable?
Olaganathan, R., Lee, A., Tong, D., Cheston, M. Z. J., & Yi, Z. H. X. (2014). Is Biofuel a Feasible Long-Term Chief Energy Source? A Global Perspective. Retrieved September 20, 2020, from https://commons.erau.edu/cgi/viewcontent.cgi?article=1920&context=publication#:~:text=Another major drawback for second,%2C a non-food crop.
Potters, G., Goethem, D. Van, & Schutte, F. (2010). Promising Biofuel Resources: Lignocellulose and Algae.
Zafar, S. (2020). Biofuels from Lignocellulosic Biomass. Retrieved September 20, 2020, from https://www.bioenergyconsult.com/what-is-lignocellulosic-biomass/
Sawdust is a tiny piece of wood that fall as powder from wood as it is cut by a saw. In other words, sawdust is basically a waste of small particles available in saw-milling industries, pulp plant and paper industries as well as wood processing industries, usually at quite large volume in form of heaps and mostly burnt off resulting in the environmental pollution (Rominiyi et al., 2017; Duanguppama et al., 2016). Sawdust is produced through the cutting, sizing, re-sawing, edging, trimming and smoothing of wood (Figure 1). In general, processing of 100 kg wood in sawmill produces around 12–25 kg sawdust (Varma and Mondal, 2016a). This biomass resource a 2nd generation resource (Ahorsu et al., 2018). Currently, sawdust is mainly used for manufacture of particle board in paper mills, although it has potential for releasing heat energy (Varma et al., 2019). In many cases due to lack of better ways of handling, this waste is commonly disposed into the environment without any treatment. Common disposal methods include heaping at the mill sides, open air combustion, disposal along roadside and water bodies. Abandonment of sawdust at saw mills causes aesthetic impacts; burning results in the environmental pollution; while abandonment along the road side causes air quality impact as a result of wind, which often blows and suspends the wood dusts into the atmosphere. This practice causes respiratory problem in human and air pollution (Ohimain, 2012; Rominiyi et al., 2017). However, these problems can be overcome by using this waste biomass to transform its internal energy into usable forms of energy through thermal conversion processes. Combustion (burning), gasification and pyrolysis are three fundamental thermal conversion processes. (Varma et al., 2019). Combustion is a simple thermal decomposition process produces heat for power generation. However, as per environmental point of view it is not a reliable process because, it generates high content of carbon dioxide and other harmful gases, and also the thermal efficiency of this process is low. Gasification is very efficient process and produces syngas (CO + H2), but it has the disadvantage of requiring high investment cost (Kumar et al., 2008). However, pyrolysis is an attractive process as it is simple to operate and inexpensive (Bridgwater, 2003). During last few years, pyrolysis process has received much attention as it produces energy in the form solid (bio-char), liquid (bio-oil) and gases from biomass/wastes by heating in inert atmosphere (Bartocci et al., 2018; Yang et al., 2006). Biomass types and their particle size, reactor types, operating parameters such as pyrolysis temperature, heating rate and vapour residence time determine the composition and yield of the products In pyrolysis process (Lu et al., 2009). For the pyrolysis of different biomass/ wastes have been used Several reactors like continuous, semi batch and batch types (Shadangi and Mohanty, 2014; Abnisa et al., 2013; Azargohar et al., 2013; Arami-Niya et al., 2011; Salehi et al., 2009). Continuous reactors are those that give higher liquid yield as compare to batch or semi batch reactor. Although the complexity of the process and control are very high in the continuous reactor, the design of these reactors needs detailed knowledge of the process. Furthermore, for any new biomass, batch or semi batch reactors are employed to explore the characteristics of process as well as generate the kinetic data which are essential for reactor design. A semi batch reactor, however, allows partial filling of reactants with the flexibility of adding more as time progresses (Varma et al., 2019).
Figure 1. Wood sawmills
In pyrolysis, the yield of bio-oil initially increases with increasing temperature, reaches the optimum at the intermediate temperature of 500 C and decreases thereafter, , the gaseous products yield rises and bio-char yield reduces continuously with increase in temperature. Bio-char yield increases and gaseous products yield reduces with rise in Wood sawdust particle size. Considering that the yield of the bio-oil is not appreciably affected by the particle size, although the maximum yield of the bio-oil is observed for the size of the intermediate particles of the biomass. Gaseous products yield rises with the rise in N2 flow rate, whereas bio-char yield decreases. However, bio-oil yield initially rises with the rise in N2 flow rate, achieves optimum value and decreases thereafter with increase in N2 flow rate (Varma et al., 2019).
Several properties of bio-oil mean that it can be used as an energy fuel after refining and improvement and, in addition, as a feedstock for important synthetic compounds. Bio-char can also be used as a solid fuel and antecedent for activated carbon. It also helps in rise of crop production through soil acidity neutralization. Wood sawdust is a good potential renewable energy source for pyrolysis, this can be supported if all the pyrolysis products are used proficiently (Varma et al., 2019).
Ahorsu, R., Medina, F., Constantí, M. (2018). Significance and Challenges of Biomass as a Suitable Feedstock for Bioenergy and Biochemical Production: A Review. Departament d’Enginyeria Química, Universitat Rovira i Virgili, 43007 Tarragona, Spain; firstname.lastname@example.org (R.A.); email@example.com (M.C.).
Rominiyi, O.L., Adaramola, B.A., Ikumapayi, O.M., Oginni, O.T. and Akinola, S.A. (2017) Potential Utilization of Sawdust in Energy, Manufacturing and Agricultural Industry; Waste to Wealth. World Journal of Engineering and Technology, 5, 526-539.
Varma, A.K., Thakur, L.S., Shankar, R., Mondal, P. (2019) Pyrolysis of wood sawdust: Effects of process parameters on products yield and characterization of products. Waste Management 89 (2019) 224–235.
Biogas production and use is one of many ways to tackle the ongoing climate crisis. Biogas can be produced in small farm-scale plants for own personal electricity use up to the scale of large plants who can produce up to 150GWh of energy. (Swedish Gas Association, 2018)
Biogas is a gas mixture that consists of mainly methane and carbon oxide with smaller proportions of hydrogen, hydrogen sulfide, nitrogen, ammonia and oxygen. It is most commonly produced from anaerobic digestion, which allows organic compounds to convert to biogas through microorganisms breaking down the compound with help of oxygen. The biogas can then be used for heat production or combusted in an engine to produce electricity. (Chang, 2018)
There are many biomass resources who can be used when producing biogas, so I decided to investigate and see which biomass resource who was considered to have the biggest potential for producing biogas.
Manure, or waste from animals is a second generation (2G) biofuel who is representing the largest resource for biogas production (Korbag, et al, 2020). Manure is also identified to be the best source for production of biogas according to a report from Lund University in 2016, which can be seen in Table 1 below (Swedish Gas Association, 2018).
Biogas production from manure is a great way to transform waste material into something valuable and usable. It is acknowledged to be one of the more energy efficient and environmentally favourable technology for bioenergy generation. After the manure has been extracted of biogas the residues can be used as fertilizer. (Korbag, et al)
But are there any disadvantages with manure as a resource for biogas production?
Manure has high water content, this leads to challenges regarding logistics and transportation which is a big limiting factor for many biofuels competing with fossil fuels in an economic perspective (Chang, 2018). Even more challenging when studies have shown that the storage of manure is decreasing the methane potential when being stored, with up to 37% after 120 days in storage (Atelge, et al, 2018). To eliminate these problems efforts are being made to use the same infrastructure as natural gas uses to connect users through this gas network and buy biogas virtually in the same way we buy renewable electricity, and eventually phase out the natural gas to it being only biogas in the infrastructure. (Sweden Gas Association, 2018).
Overall, I think biogas production is a versatile and promising way forward to reduce and replace the use of fossil fuels in power and heat production, and fuel for vehicles. Which will reduce our negative impact on the climate with greenhouse gas emissions and substitute conventional sources for energy.
To conclude this all, I personally think we can expect biogas production and use to be a part in the search and development for renewable and sustainable energy in the future.
Swedish Gas Association. (2018). NATIONAL BIOGAS STRATEGY 2.0. Available from: https://www.energigas.se/library/2303/national-biogas-strategy-2_0.pdf
Cheng, J. (2018). Biomass to renewable energy processes (second edition). CRC Press.
Issa Korbag., Salma Mohamed Saleh Omer., Hanan Boghazala., & Mousay Ahmeedah Aboubakr Abusasiyah. (2020). Recent Advances of Biogas Production and Future Perspective. DOI: 10.5772/intechopen.93231
M. R. Atelge., David Krisa., Gopalakrishnan Kumar., Cigdem Eskicioglu., Dinh Duc Nguyen., Soon Woong Chang., A. E. Atabani., Alaa H. Al-Muhtaseb., & S. Unalan. (2018). Biogas Production from Organic Waste: Recent Progress and Perspectives. https://doi.org/10.1007/s12649-018-00546-0
All around the world, oil has been variously used for cooking purposes for centuries. Its major use, is as a medium for heat transfer when frying and of course as an additive for flavour and texture. There is a big variety of cooking oils derived from plants such as olive, sunflower and rapeseed that are mostly used in Europe, or soybean and palm oil that are widely used in south America and south-east Asia. In addition, butter and lard are considered as animal-based cooking oils. However, cooking oil does not stop being useful after being fried. Used cooking oil is considered a low-cost and renewable feedstock for the production of biodiesel and other biobased products.
Europe and many individual countries have set goals regarding the climate change. Moreover, Sweden aims to be the first country that will become fossil free in the transportation sector by 2030. Thus, renewable fuels have become one of the main pillars to succeed such a goal. Vegetable oil is an already commercial used feedstock for the production of different renewable fuels such as biodiesel or hydrotreated vegetable oil (HVO). However, the use of such an edible feedstock is competing with food industry and poses the global dilemma of the need of feeding humanity versus the exploitation of land for agro-energy. Such a dilemma can be avoided with the use of used cooking oil (UCO) instead. Since the oil has already been used for cooking purposes it is considered a waste, hence the biofuels produced from UCO are as stated “second generation” biofuels.,
During the last decade a significant increase in the usage of UCO has been reported in Europe. Even though rapeseed oil (RO) still remains the dominant biodiesel raw material, its share in the feedstock mix has decreased from 72% in 2008 to 47% in 2016. This is due to the use of recycled cooking oil that has become the second most important feedstock in Europe accounting to 18% in 2016. In Figure 1. a simplified process flow is illustrating the upgrade of waste oils to Hydrotreated Vegetable Oils (HVO) such as kerosene as a renewable jet fuel or green diesel as a renewable fuel used in the transport section. As it can be seen from the figure the UCO needs to be pretreated before the phase of hydrotreatment where hydrogen is added. Based on the feedstock green diesel could be classified as biodiesel, however, based on the processing technology and chemical formula green diesel and biodiesel are different products.,,
Overall, as presented UCO exploitation can involve large reductions in life cycle impacts, cutting the need for virgin vegetable oil for fuel production and promoting a way of waste management for this type of waste. Furthermore, some additional advantages of this biomass resource are that it can be found in abundance and since it is waste that is non-edible anymore it does not longer compete with food. Finally, it is a feedstock that depending on the chosen method can produce a variety of bio-products. Despite UCO seems to be an attractive choice of feedstock, there are some challenges that need to be overcome. Firstly, the supply chain plays a major role in the sustainability of the proposed production schemes, hence life cycle assessment of the feedstock must be done to examine the environmental impacts of the feedstock from its harvest to the collection point of UCO and it is necessary to deploy effective policies and regulated practices to enhance UCO recycling and collection rates, under multistakeholder considerations. Moreover, UCOs have a highly heterogenous nature, depending their origin, that make them having a big variety of different properties (i.e physicochemical, impurities, color, odor), thus the right pre-treatment method must be chosen.
In the quest of creating carbon-neutral societies and end our dependence on oil, many countries have started to look at biofuels derived from renewable biomass as an alternative to fossil fuels. A significant source of greenhouse gas emissions stemming from human activities is the transport sector, currently accounting for approximately 25% of emissions in the European Union (Eurostat, 2020). In order to reduce this share, the EU introduced a renewable energy directive in 2009, recently revised for 2030 where a minimum of 14% of the fuel used in the transport sector must consist of renewables (European commission, 2020).
This new goal might seem ambitious, but all biofuels are not equal in terms of environmental performance. Significant portions of the biofuel share are currently made up of so-called first-generation biofuels directly made from food crops such as rapeseed, soy, sugarcane, wheat and corn. The cultivation of these edible feedstocks has sparked controversy over the years with issues such as aggressive agricultural land expansion, food security issues and higher than expected cumulative GHG emissions. The EU therefore included a provision in the energy directive where at least 3,5 % of the used biofuels must be based on non-food feedstock in 2030 (European commission, 2020a).
Replacing the first-generation biofuels will not be an easy task. Second generation biofuels mainly produced from non-edible lignocellulosic materials and miscellaneous waste is not as well established in all countries. Varying regional feedstock availability and composition further compound the issue. How can we increase the share of advanced biofuels in the immediate future and meet the rapidly approaching environmental targets? Large quantities of sustainable biofuels are going to be needed that can seamlessly be included in the existing transport infrastructure.
This is where hemp comes into the picture. Industrial hemp, a non-psychoactive variant of the Cannabis sativa plant is a fast-growing biomass that has a multitude of uses. From clothing, paper and plastics to construction materials and cosmetics, the list is nearly endless. Hemp is also one of the earliest domesticated plants, dating back more than 8000 years over multiple continents and climatic zones, so the experience in its cultivation is there.
Advantages of hemp as an energy crop is the low water requirements, strong weed competitiveness, high disease resilience leading to low pesticide demand and a short three-month life cycle making it suitable for crop rotations during the winter. Hemp also recirculates approximately 70% of its nutrients back into the soil, drastically reducing the amount of needed fertilizer. An added benefit of hemp cultivation is also the prevention of soil erosion due to its long and fast-growing roots (Alcheikh, 2015).
A further benefit to the soil is the plant’s ability to restore them from toxic pollution, so-called phytoremediation where contaminants are absorbed by the roots of a plant capable of accommodating toxins and heavy metals (Ahmad et al., 2016). An example of this effect is the growth of hemp surrounding the Chernobyl nuclear plant where it is used to remove radioactive elements from the soil and water (Dushenkov et al., 1998). This overall resilience combined with the low nutrient and water requirements makes it a compelling feedstock for second generation biodiesel, ethanol, methanol and biogas.
The whole plant can be used in the creation of biofuels. The seeds contain around 30% oil which can be used in transesterification processes to generate biodiesel with lower sulfur content compared to soybean and rapeseed-based biodiesel (Alcheikh, 2015 p.18). The rest of the plant can be used to produce hemp equivalents of ethanol and methanol, so called hempanol or hempoline (MHFMA, nd) or biogas through anaerobic digestion.
There are downsides to hemp as a biomass though. The economic viability may be called into question due to the versatile nature of the plant. Many products with a higher return on investment can be produced from hemp making biofuel production less attractive to farmers. Furthermore, the issues surrounding land use are only partially addressed with hemp. Arable land will still be used for monocultures of hemp and yields will be higher on fertile soil compared to cultivation on marginal land. Legal issues also remain due to the similarities between industrial hemp and marijuana. The United States banned industrial hemp production in 1937 with the rest of the world following suit soon after. In recent years, the worldwide bans have been gradually lifted but the long hiatus has led to very low levels of current production.
Industrial hemp might not be the end-all or perfect biomass but as a transitional source of biofuel it holds a lot of promise and should be further investigated if we intend to live up to the impending environmental goals.
Ahmad, R., Tehsin, Z., Malik, S.T., Asad, S.A., Shahzad, M., Bilal, M., Shah, M.M. and Khan, S.A., 2016. Phytoremediation Potential of Hemp (Cannabis sativa L.): Identification and Characterization of Heavy Metals Responsive Genes: Biotechnology. CLEAN – Soil, Air, Water, 44(2), pp.195–201.
European commission, 2020. Renewable Energy Directive. Available at: https://ec.europa.eu/energy/topics/renewable-energy/renewable-energy-directive/overview_en
European commission 2020a. Renewable Energy – Recast to 2030 (RED II). Available at: https://ec.europa.eu/jrc/en/jec/renewable-energy-recast-2030-red-ii
Eurostat, 2020. Greenhouse gas emission statistics – emission inventories. Available at: https://ec.europa.eu/eurostat/statistics-explained/pdfscache/1180.pdf
Minnesota Hemp Farmers & Manufacturers Association (MHFMA) n.d. Environmental Benefits of Hemp. MHFMA. Available at: https://www.mhfma.mn/resources/environmental-benefits-of-hemp/
Slavik Dushenkov, *, Alexander Mikheev, ‡, Alexei Prokhnevsky, ‡, Michael Ruchko, ‡ and and Sorochinsky‡, B., 1998. Phytoremediation of Radiocesium-Contaminated Soil in the Vicinity of Chernobyl, Ukraine. [research-article] Available at: https://pubs.acs.org/doi/10.1021/es980788%2B
Rising temperatures, melting glaciers, forest fires and devastating storms. To my belief, there is finally a consensus in developed countries to realize the threats of global warming. We know what happens, but what we should do to stop it is not so obvious. It is likely that fossil fuels for energy will slowly be phased out and replaced by options considered cleaner. Whether the replacement is nuclear, solar, hydro, wind power, energy from biomass or a mixture of these is uncertain; what I think will determine the outcome is mainly the economic viability of these options and how well they can compete with fossil energy sources.
I am certain that bioenergy belongs to the future and that the supply and demand will continue to increase. However, it is not so sure if bioenergy will be able to directly compete with fossil energy and other renewables in the long run. The bulk of the future transport sector in leaning more towards battery and fuel cell vehicles than biofuel powered options. Blending levels of biofuels in fossil based fuel might also not increase as much as expected if oil prices drop, as was observed as the covid-19 crisis lowered the global energy demand by 3.8% in Q1 2020 (1). Bioenergy for electricity shows promise but how clean is it really compared to renewables such and solar and wind?
What I believe is that biomass for energy will not compete with, but will serve as a complement to other energy sources. I think mainly we should focus on biomass which serve more purposes than generating energy, or biomass which is used in applications where no better options exist. This brings me to the intended topic of this blog post: second generation biomass and more specifically food waste, which is an example of the class of biomass which I think holds most potential based on the technology available today.
About one third of all food produced globally is being wasted, amounting to 1.3 billion tonnes of food in 2017 (2). Food waste is thus an abundant resource which offers great potential as an energy source. What I really like about food waste is that it serves yet another purpose. Apart from converting biomass into a refined energy source, it is part of a sustainable solution to the problems related to waste disposal. Food waste contains biomolecules such as proteins, carbohydrates and lipids and can for example be used as a substrate in anaerobic fermentation by microbes into a variety of refined products such as hydrogen, ethanol, and methane (3)(Figure 1).
I think food waste is a very good example of a biomass which serves multiple purposes (both waste disposal and energy source) and can be utilized in applications where options are limited. This is because by anaerobic fermentation, food waste can be refined into for example methane, the main component of biogas (3). Biogas is not likely to be a realistic competitor for fossil fuels or electricity to power our private vehicles, but it serves as a good complement as a fuel for heavy transportation. Obviously fossil fuels are not preferable, todays batteries do not have the capacity to power heavy vehicles and other liquid biofuels are struggling with compatibility in combustion engines (4). Biogas can be considered a sustainable and economically viable option as fuel for heavy-duty vehicles such as buses (5). When liquified, biogas can also be considered as a marine fuel (6). As the shipping sector is a large contributor to greenhouse emissions and air pollution, I think this sector is very important for alternatives such as biofuels to take over.
It is worth to mention that I don’t think that producing biogas from food waste will save the planet. The problem is obviously much bigger, and efforts should mainly be concentrated to stop the overconsumption of food products in developed countries and to the reduce large amount of waste generated in the food-production and distribution chain.
1. Renewables – Global Energy Review 2020 – Analysis – IEA [Internet]. [cited 2020 Sep 20]. Available from: https://www.iea.org/reports/global-energy-review-2020/renewables#abstract
2. Paritosh K, Kushwaha SK, Yadav M, Pareek N, Chawade A, Vivekanand V. Food Waste to Energy: An Overview of Sustainable Approaches for Food Waste Management and Nutrient Recycling. Vol. 2017, BioMed Research International. Hindawi Limited; 2017.
3. Dahiya S, Kumar AN, Shanthi Sravan J, Chatterjee S, Sarkar O, Mohan SV. Food waste biorefinery: Sustainable strategy for circular bioeconomy. Vol. 248, Bioresource Technology. Elsevier Ltd; 2018. p. 2–12.
4. Motorists face huge repairs bill as Government biofuels destroy engines | Daily Mail Online [Internet]. [cited 2020 Sep 20]. Available from: https://www.dailymail.co.uk/news/article-564154/Motorists-face-huge-repairs-Government-biofuels-destroy-engines.html
5. Cong RG, Caro D, Thomsen M. Is it beneficial to use biogas in the Danish transport sector? – An environmental-economic analysis. J Clean Prod. 2017 Nov 1;165:1025–35.
6. Brynolf S, Fridell E, Andersson K. Environmental assessment of marine fuels: Liquefied natural gas, liquefied biogas, methanol and bio-methanol. J Clean Prod. 2014 Jul 1;74:86–95.
When talking about environmental problems and solutions there’s no single answer. It’s a complex, multifaceted problem and people on an individual level to global companies and nations have an effect on our environment. Biomass fuel can be a part of the solution to the growing problems. Biomass don’t just consist of one material, there’s many different kind of fuels and different grades. One type of fuel that has a big importance is municipal and industrial waste which is a second grade biomass fuel. The reason why this fuel is important is because everybody on our planet contributes waste products and to be able to use those waste products to gain energy and heating can be beneficial but it also has a lot of problems.
In Sweden industrial and municipal waste products are used to heat buildings with district heating. In 2014 waste products amounted to 22% of the total amount of fuel that was burned in district heating plants. One of the problems with Sweden’s use of waste for district heating is that a large amount of the waste used is imported, almost one third is imported, mostly from Norway and Britain. The importation of the waste contributes to the global warming because almost all means of transportation consumes fossil fuels. Another problem is that the ash that’s left after burning the waste is toxic. The toxic ash is transported back to Norway where it’s stored in a limestone quarry on the island Langøya. (Naturskyddsföreningen 2016).
The reason why we use waste products as fuel is because it’s considered better than storing it in a landfill waste. According to a EU waste hierarchy the EU countries should:
– Minimize the amount of waste generated
– Reuse as much as possible
– Recycle. If possible recycle the material and if not possible recycle the energy.
– Store the waste in a landfill
Being able to recycle the energy in the materials generates heating to around 1 million homes in Sweden. (Avfall Sverige 2020).
It’s hard to judge if using waste is a good solution from an environmental perspective. It’s better than storing waste in a landfill according to EU directives but that doesn’t say much in my opinion. Importing waste and exporting toxic ash like we do in Sweden seems counterproductive and there’s got to be a better solution than the current system in place. I believe that the biggest problem isn’t recycling the energy in the waste, the problem is the amount of waste that we generate and the waste that cant be recycled or reused as material. We recycle the energy in the materials because there’s no better solution and if we instead reduced the waste and made more products that could be recycled that would be a better way to reduce our environmental impact.
Naturskyddsföreningen (2016). Högt miljöpris för sopimport. Downloaded 2020-09-20 from: https://www.naturskyddsforeningen.se/sveriges-natur/2016-3/hogt-miljopris-sopimport
Avfall Sverige (2020). Energiåtervinning. Downloaded 2020-09-20 from: https://www.avfallsverige.se/avfallshantering/avfallsbehandling/energiatervinning/
In this blog we will discuss some interesting aspects of microalgae, advantages and what barriers are necessary to cross in order to use these microorganisms as a sustainable energy source. Microalgae are unicellular microorganisms capable of photosynthesis. That is, they are capable of generating organic biomass from CO2 (as an inorganic source of carbon) and light (as an energy source). It is a 3G energy source.It is important to know that not all species of algae are suitable for the production of biodiesel. There is currently no known algae strain that can be considered the best in terms of oil yield for obtaining biodiesel, but the Porphyridium cruentum strain is a good example of the potential that some strains have .
The research that has been carried out over the last 50 years has shown that microalgae are capable of producing a wide range of chemical intermediates and hydrocarbons that offer the possibility of replacing petroleum or natural gas products. Three main components can be extracted from the biomass of the microalgae: lipids (including triglycerides and fatty acids), carbohydrates, and proteins. The bioconversion of these products into alcohols, methane, hydrogen, organic acids and the catalytic conversion of paraffins, olefins and aromatic compounds, make the exploitation of microalgae a true biorefinery industry.
It has many advantages over its competitors obtained from crops for food consumption:
-Independent of arable land.
-High productivity per unit area. Unlike other oil crops, algae grow exponentially (doubling every 8 hours or so).
-High levels of production under controlled conditions; which implies the possibility of being cultivated throughout the year.
-It is not a food resource. Therefore, it does not compete with agricultural activities.
-Use of a wide range of water sources. Water used for algae cultivation can include sewage and non-potable brackish water that cannot be used for either conventional agriculture or domestic use.
-Mitigation of the release of GHG into the atmosphere. Algae have enormous potential to reduce greenhouse gas emissions through the use of CO2-rich gas streams from thermal power plants and natural gas recovery operations.
-No competitive cost. It requires technological development to lower the current price of biodiesel. The Cyclag project, in which 6 research centers in France and Spain have participated, estimates that biodiesel could be obtained from cultivated microalgae for a value of 3.3 $ / l.
-Lack of aid. It requires incentives or subsidies from governments for the development of techniques that lowers the cost.
-A joint cooperation between the research centers of these crops is necessary, since at present the lack of transparency of these centers is slowing down their development.
Microalgae are an alternative for obtaining biodiesel due to its high lipid yield and its fatty acid profile. This would mean extending the useful life of diesel vehicles, reducing the pollution caused by fossil fuels.
Sweden has an advantage over other countries, it has many aquifers that can be used for both closed and open systems. This energy source provides another possibility to achieve an independent national transport of fossils by 2030.
As we have seen, the advantages outweigh the disadvantages. However, the economic barrier (achieving lower production costs) makes this fuel unfeasible at present.
 Tredici, M.R., Biotechnology and Applied Phycology (2004)
 Biofuels from algae: Technology options, energy balance and GHG emissions. Insights from a literature reviem EUR 27582
 U.S.DOE 2010: “National Algae Biofuels Technology Roadmap”. U.S Department of Energy, Office of Energy Efficiency and Renowable Energy, Biomass Program
 I.Priyadarshani, B.Rath: ”Commercial and industrial applications of micro algae – A review” . J.Algal Biomass Utln. 2012, 89-100
Biomass can provide energy in a million different ways – some more advantageous than others. Locally produced biogas from sewage and farming waste is a biofuel that I see the largest potential in because it combines many advantages. Briefly put these are the short transport distances in all steps of the process, the improvement of circularity due to efficient use of a waste product and the low impact on arable land.
Compared to fossil fuels, the energy density of any biomass is lower (Cheng, 2018), so minimal transport is one key factor in making energy production from biomass viable. Modern towns and cities have municipal sewage treatment plants and an extension to include biogas production completely erases transport. A vehicle fuel station can be built just outside where the gas is produced which is often just on the edge of a city, a reasonable distance for people to drive to fill up their cars. Alternatively, biogas can be produced at farms as Eliasson describes (2018) or farm waste could be collected and added to the sewage sludge to increase the amount of biogas that can be produced. This would of course mean that some transport is necessary but compared to the transport footprint of fossil fuels this would still be minimal.
Using a by-product of agriculture or a waste product like sewage sludge as a biomass feedstock means it can be classified as a second-generation resource. Second-generation resources don’t require arable land like first-generation resources, but this comes at a cost. Unlike first- and third-generation resources, second-generation feedstocks are not produced for the purpose of energy conversion which means that suitability and energy content can be lower. Nevertheless, using a waste product enhances circularity of agricultural and water treatment systems by decreasing the amount of virgin biomass or other external inputs required (e.g. fossil fuels) and thereby promoting positive climate impact.
The potential to expand biogas production in Sweden is great because there are many incentives from policies that encourage the investment in fossil-free fuels as well as tax exemptions (Lönnqvist et al, 2015). However, biogas plants are still a heavy investment and they may be difficult to shoulder for smaller municipalities. The map illustrates the spread of vehicle gas stations across Sweden and shows that – unsurprisingly – the majority are found in the south. Nonetheless, I have experienced that many people north of Stockholm frequently drive much longer distances than what’s common in the south, which makes investment in biogas plants in remote areas just as valuable as plants in the well populated south.
An issue that has been identified in several studies has been the fact that manure and sewage sludge have relatively low energy contents and the degradation and gas production can be slow. Co-digestion has therefore been proposed where energy crops (Eliasson, 2018) or microalgae (Thorin et al, 2017) are added to provide higher gas yields.
Altogether, locally produced biogas from sewage sludge is a viable biofuel that is a step towards making a city independent from fossil fuel deliveries from half-way across the world.
Cheng, J. (2018). Biomass to renewable energy processes (second edition). CRC Press.
Eliasson, K. A. (2018). Swedish farm-scale biogas production-substrates and operating parameters. (Doctoral Thesis, SLU, Uppsala). Retrieved from https://pub.epsilon.slu.se/15821/8/ahlberg_eliasson_k_190107.pdf
Hitta tankstation | Här tankar du biogas och fordonsgas i Västsverige. (n.d.). FordonsGas. Retrieved 20 September 2020, from https://fordonsgas.se/tanka-gas/gasstationer/
Lönnqvist, T., Sanches-Pereira, A., & Sandberg, T. (2015). Biogas potential for sustainable transport – a Swedish regional case. Journal of Cleaner Production, 108, 1105–1114. https://doi.org/10.1016/j.jclepro.2015.07.036
Thorin, E., Olsson, J., Schwede, S., & Nehrenheim, E. (2017). Biogas from Co-digestion of Sewage Sludge and Microalgae. Energy Procedia, 105, 1037–1042. https://doi.org/10.1016/j.egypro.2017.03.449