Cities around the world produce huge quantity of municipal wastewater (or sewage) which represents a serious problem due to its high treatment costs and risk to environment, human health and marine life. Sewage generation is bound to increase at rapid rates due to increase in number and size of urban habitats and growing industrialization.
An attractive disposal method for sewage sludge is to use it as alternative fuel source in cement industry. The resultant ash is incorporated in the cement matrix. Infact, several European countries, like Germany and Switzerland, have already started adopting this practice for sewage sludge management. Sewage sludge has relatively high net calorific value of 10-20 MJ/kg as well as lower carbon dioxide emissions factor compared to coal when treated in a cement kiln.
Use of sludge in cement kilns can also tackle the problem of safe and eco-friendly disposal of sewage sludge. The cement industry accounts for almost 5 percent of anthropogenic CO2 emissions worldwide. Treating municipal wastes in cement kilns can reduce industry’s reliance on fossil fuels and decrease greenhouse gas emissions.
The use of sewage sludge as alternative fuel in clinker production is one of the most sustainable option for sludge waste management. Due to the high temperature in the kiln the organic content of the sewage sludge will be completely destroyed. The sludge minerals will be bound in the clinker after the burning process. The calorific value of sewage sludge depends on the organic content and on the moisture content of the sludge. Dried sewage sludge with high organic content possesses a high calorific value. Waste coming out of sewage sludge treatment processes has a minor role as raw material substitute, due to their chemical composition.
The dried municipal sewage sludge has organic material content (ca. 40 – 45 wt %), therefore the use of this alternative fuel in clinker production will save fossil CO2 emissions. According to IPCC default of solid biomass fuel, the dried sewage sludge CO2 emission factor is 110 kg CO2/GJ without consideration of biogenic content. The usage of municipal sewage sludge as fuel supports the saving of fossil fuel emission.
Sludge is usually treated before disposal to reduce water content, fermentation propensity and pathogens by making use of treatment processes like thickening, dewatering, stabilisation, disinfection and thermal drying. The sludge may undergo one or several treatments resulting in a dry solid alternative fuel of a low to medium energy content that can be used in cement industry.
The use of sewage sludge as alternative fuel is a common practice in cement plants around the world, Europe in particular. It could be an attractive business proposition for wastewater treatment plant operators and cement industry to work together to tackle the problem of sewage sludge disposal, and high energy requirements and GHGs emissions from the cement industry.
Food residuals are an untapped renewable energy source that mostly ends up rotting in landfills, thereby releasing greenhouse gases into the atmosphere. Food residuals are difficult to treat or recycle since it contains high levels of sodium salt and moisture, and is mixed with other waste during collection. Major generators of food wastes include hotels, restaurants, supermarkets, residential blocks, cafeterias, airline caterers, food processing industries, etc.
In United States, food scraps is the third largest waste stream after paper and yard waste. Around 12.7 percent of the total municipal solid waste (MSW) generated in the year 2008 was food scraps that amounted to about 32 million tons. According to EPA, about 31 million tons of food waste was thrown away into landfills or incinerators in 2008. As far as United Kingdom is concerned, households throw away 8.3 million tons of food each year. These statistics are an indication of tremendous amount of food waste generated all over the world.
The proportion of food residuals in municipal waste stream is gradually increasing and hence a proper food waste management strategy needs to be devised to ensure its eco-friendly and sustainable disposal. Currently, only about 3 percent of food waste is recycled throughout U.S., mainly through composting. Composting provides an alternative to landfill disposal of food waste, however it requires large areas of land, produces volatile organic compounds and consumes energy. Consequently, there is an urgent need to explore better recycling alternatives.
Anaerobic digestion has been successfully used in several European and Asian countries to stabilize food wastes, and to provide beneficial end-products. Sweden, Austria, Denmark, Germany and England have led the way in developing new advanced biogas technologies and setting up new projects for conversion of food waste into energy.
Anaerobic Digestion of Food Waste
Anaerobic digestion is the most important method for the treatment of organic waste, such as food residuals, because of its techno-economic viability and environmental sustainability. The use of anaerobic digestion technology generates biogas and preserves the nutrients which are recycled back to the agricultural land in the form of slurry or solid fertilizer.
The relevance of biogas technology lies in the fact that it makes the best possible use of various organic wastes as a renewable source of clean energy. A biogas plant is a decentralized energy system, which can lead to self-sufficiency in heat and power needs, and at the same time reduces environmental pollution. Thus, anaerobic digestion of food waste can lead to climate change mitigation, economic benefits and landfill diversion opportunities.
Of the different types of organic wastes available, food waste holds the highest potential in terms of economic exploitation as it contains high amount of carbon and can be efficiently converted into biogas and organic fertilizer. Food waste can either be used as a single substrate in a biogas plant, or can be co-digested with organic wastes like cow manure, poultry litter, sewage, crop residues, slaughterhouse wastes, etc.
A Typical Food Waste-to-Energy Plant
The feedstock for the food waste-to-energy plant includes leftover food, vegetable refuse, stale cooked and uncooked food, meat, teabags, napkins, extracted tea powder, milk products, etc. Raw waste is shredded to reduce to its particle size to less than 12 mm. The primary aim of shredding is to produce a uniform feed and reduce plant “down-time” due to pipe blockages by large food particles. It also improves mechanical action and digestibility and enables easy removal of any plastic bags or cling-film from waste.
Fresh waste and re-circulated digestate (or digested food waste) are mixed in a mixing tank. The digestate is added to adjust the solids content of the incoming waste stream from 20 to 25 percent (in the incoming waste) to the desired solids content of the waste stream entering the digestion system (10 to 12 percent total solids). The homogenized waste stream is pumped into the feeding tank, from which the anaerobic digestion system is continuously fed. Feeding tank also acts as a pre-digester and subjected to heat at 55º to 60º C to eliminate pathogens and to facilitate the growth of thermophilic microbes for faster degradation of waste.
From the predigestor tank, the slurry enters the main digester where it undergoes anaerobic degradation by a consortium of Archaebacteria belonging to Methanococcus group. The anaerobic digester is a CSTR reactor having average retention time of 15 to 20 days. The digester is operated in the mesophilic temperature range (33º to 38°C), with heating carried out within the digester. Food waste is highly biodegradable and has much higher volatile solids destruction rate (86 to 90 percent) than biosolids or livestock manure. As per conservative estimates, each ton of food waste produces 150 to 200 m3 of biogas, depending on reactor design, process conditions, waste composition, etc.
Biogas contains significant amount of hydrogen sulfide (H2S) gas that needs to be stripped off due to its corrosive nature. The removal of H2S takes place in a biological desulphurization unit in which a limited quantity of air is added to biogas in the presence of specialized aerobic bacteria that oxidizes H2S into elemental sulfur. The biogas produced as a result of anaerobic digestion of waste is sent to a gas holder for temporary storage. Biogas is eventually used in a combined heat and power (CHP) unit for its conversion into thermal and electrical energy in a cogeneration power station of suitable capacity. The exhaust gases from the CHP unit are used for meeting process heat requirements.
The digested substrate leaving the reactor is rich in nutrients like nitrogen, potassium and phosphorus which are beneficial for plants as well as soil. The digested slurry is dewatered in a series of screw presses to remove the moisture from slurry. Solar drying and additives are used to enhance the market value and handling characteristics of the fertilizer.
Diverting Food from Landfills
Food residuals are one of the single largest constituents of municipal solid waste stream. Diversion of food waste from landfills can provide significant contribution towards climate change mitigation, apart from generating revenues and creating employment opportunities. Rising energy prices and increasing environmental pollution makes it more important to harness renewable energy from food scraps.
Anaerobic digestion technology is widely available worldwide and successful projects are already in place in several European as well as Asian countries that makes it imperative on waste generators and environmental agencies to root for a sustainable food waste management system.
Most, if not all of Europe has a suitable climate for biogas production. The specific type of system depends on the regional climate. Regions with harsher winters may rely more on animal waste and other readily available materials compared to warmer climates, which may have access to more crop waste or organic material.
Regardless of suitability, European opinions vary on the most ethical and appropriate materials to use for biogas production. Multiple proponents argue biogas production should be limited to waste materials derived from crops and animals, while others claim crops should be grown with the intention of being used for biogas production.
Biogas Production From Crops
Europeans in favor of biogas production from crops argue the crops improve the quality of the soil. Additionally, they point to the fact that biogas is a renewable energy resource compared to fossil fuels. Crops can be rotated in fields and grown year after year as a sustainable source of fuel.
Extra crops can also improve air quality. Plants respire carbon dioxide and can help reduce harmful greenhouse gasses in the air which contribute to global climate change.
Energy crops can also improve water quality because of plant absorption. Crops grown in otherwise open fields reduce the volume of water runoff which makes it to lakes, streams and rivers. The flow of water and harmful pollutants is impeded by the plants and eventually absorbed into the soil, where it is purified.
Urban residents can also contribute to biogas production by growing rooftop or vertical gardens in their homes. Waste from tomatoes, beans and other vegetables is an excellent source of biogas material. Residents will benefit from improved air quality and improved water quality as well by reducing runoff.
Proponents of biogas production from crops aren’t against using organic waste material for biogas production in addition to crop material. They believe crops offer another means of using more sustainable energy resources.
Biogas Production From Agricultural Waste
Opponents to growing crops for biogas argue the crops used for biogas production degrade soil quality, making it less efficient for growing crops for human consumption. They also argue the overall emissions from biogas production from crops will be higher compared to fossil fuels.
Growing crops can be a labor-intensive process. Land must be cleared, fertilized and then seeded. While crops are growing, pesticides and additional fertilizers may be used to promote crop growth and decrease losses from pests. Excess chemicals can run off of fields and degrade the water quality of streams, lakes and rivers and kill off marine life.
Once crops reach maturity, they must be harvested and processed to be used for biogas material. Biogas is less efficient compared to fossil fuels, which means it requires more material to yield the same amount of energy. Opponents argue that when the entire supply chain is evaluated, biogas from crops creates higher rates of emissions and is more harmful to the environment.
Agricultural residues, such as rice straw, are an important carbon source for anaerobic digestion
In Europe, the supply chain for biogas from agricultural waste is more efficient compared to crop materials. Regardless of whether or not the organic waste is reused, it must be disposed of appropriately to prevent any detrimental environmental impacts. When crop residues are used for biogas production, it creates an economical means of generating useful electricity from material which would otherwise be disposed of.
Rural farms which are further away from the electric grid can create their own sources of energy through biogas production from agriculture wastes as well. The cost of the energy will be less expensive and more eco-friendly as it doesn’t have the associated transportation costs.
Although perspectives differ on the type of materials which should be used for biogas production, both sides agree biogas offers an environmentally friendly and sustainable alternative to using fossil fuels.
Biomethane, also known as the green gas, is a well-known and well-proven source of clean energy, and is witnessing increasing demand worldwide, especially in European countries, as it is one of the most cost-effective and eco-friendly replacement for natural gas and diesel.
Advantages of Biomethane
The key advantage of biomethane is that it is less corrosive than biogas which makes it more flexible in its application than raw biogas. It can be injected directly into the existing natural gas grid leading to energy-efficient and cost-effective transport, besides allowing natural gas grid operators to persuade consumers to make a smooth transition to a renewable source of natural gas.
Biogas can be upgraded to biomethane and injected into the natural gas grid to substitute natural gas or can be compressed and fuelled via a pumping station at the place of production. Biomethane can be injected and distributed through the natural gas grid, after it has been compressed to the pipeline pressure.
The injected biomethane can be used at any ratio with natural gas as vehicle fuel. In many EU countries, the access to the gas grid is guaranteed for all biogas suppliers.
A major advantage of using natural gas grid for biomethane distribution is that the grid connects the production site of biomethane, which is usually in rural areas, with more densely populated areas. This enables biogas to reach new customers.
Storage of Biomethane
Biomethane can be converted either into liquefied biomethane (LBM) or compressed biomethane (CBM) in order to facilitate its long-term storage and transportation. LBM can be transported relatively easily and can be dispensed through LNG vehicles or CNG vehicles. Liquid biomethane is transported in the same manner as LNG, that is, via insulated tanker trucks designed for transportation of cryogenic liquids.
Biomethane can be stored as CBM to save space. The gas is stored in steel cylinders such as those typically used for storage of other commercial gases.
Applications of Biomethane
Biomethane can be used to generate electricity and heating from within smaller decentralized, or large centrally-located combined heat and power plants. It can be used by heating systems with a highly efficient fuel value, and employed as a regenerative power source in gas-powered vehicles.
Biomethane, as a transportation fuel, is most suitable for vehicles having engines that are based on natural gas (CNG or LNG). Once biogas is cleaned and upgraded to biomethane, it is virtually the same as natural gas.
Because biomethane has a lower energy density than NG, due to the high CO2 content, in some circumstances, changes to natural gas-based vehicle’s fuel injection system are required to use the biomethane effectively.
Wide-spread environmental concerns about plastic waste are leading to increased demand for the plastic recycling (PR) market that has various uses for plastic waste. At the same time, and in line with this growing need, an increased number of industries that produce plastic products have committed to reducing their use of virgin plastic and ensuring that the plastic they do produce is recyclable, reusable, or compostable.
Growth of the Plastic Recycling Market
Valued at around $43.73 billion in 2018, research indicates that the plastic recycling market will grow at a compound annual growth rate (CAGR) of 6.6% in revenue and 8.8% in volume by 2027. Findings are that rising environmental concerns will be the primary driving force along with the concerted global effort towards effective waste management and sustainability. Another is the growing awareness of the need for recycling plastic and the anticipated market growth of the PR market.
A new report released by Research and Markets in February 2020 gives a market snapshot in its executive summary and discusses the plastic recycling market by material type, source, application, and geography. Titled Global Plastic Recycling Market Size, Market Share, Application Analysis, Regional Outlook, Growth Trends, Key Players, Competitive Strategies and Forecasts, 2019 to 2027, it explores the roles of the many global and regional participants in the PR market and analyses anticipated acquisitions, partnerships, and collaborations. These, the report states, are likely to be the major strategies market players will follow in an endeavor to expand their geographic presence and market share.
An older report published mid-2018 gave a slightly lower CAGR for the period 2018 to 2023 of 4.3%. This report, Global Plastic Waste Management Market 2018 by Manufacturers, Regions, Type and Application, Forecast to 2023 stated that it would grow from an estimated $27,1000 in 2017 to $34,900 in 2023.
When research for the new report was carried out during 2018, the Asia-Pacific region including China, Indonesia, Malaysia, and India, had the highest market share in plastic recycling. This was attributed to the fact that the region has the largest share in the generation of plastic waste and is also the biggest plastic waste importer.
However, Europe was pinpointed as a region poised to become the fastest-growing in the PR market due to increasing government initiatives and the improvement of recycling facilities in this part of the world.
While the report covers at least 16 companies involved in plastic recycling globally, the Hungarian MOL Group has been highlighted as a result of its acquisition of Aurora, a German recycled plastic compounder company. MOL is a well-established supplier of virgin polymers and was motivated by its Enter Tomorrow 2030 strategy that aims to move its business from a traditional fuel-based model to a higher value-added petrochemical product portfolio. More specifically, MOL intends to strengthen its position as a supplier in the sustainable plastic compounding segment of the automotive industry.
The older report focused on plastic waste management not only in the Asia-Pacific region but also in North and South America, Europe, the Middle East, and Africa.
Use of Recycled Plastic
In terms of plastic materials, high-density polyethylene (HDPE) and polyethylene terephthalate (PET) had the biggest market share in 2018. The reason given for this was a rapid surge in demand for PET and HDPE for the manufacturing of packaging. Hopefully, this won’t increase the production of PET and HDPE, but will rather help to get rid of waste.
As the CEO of Unilever, Alan Jope, said in a press statement late 2019: “Plastic has its place, but that place is not in the environment.” He was announcing Unilever’s commitment to halve its use of virgin plastic, reduce its use of plastic packaging, and dramatically step up its use of recycled plastic by 2025. They would also help to collect and process more plastic packaging than it sells – which will amount to about 600,000 tonnes per year, he said.
Additionally, technological advances in the PR industry have led to other less expected uses including the manufacture of denim clothing.
Realizing the environmental impact production of denim clothing has, Levi Strauss & Co. has taken bold steps to reduce its use of water and chemicals in cotton and cotton-clothing production, and about a decade ago, the company launched its much more sustainable Water<Less range of jeans. In 2013, Levi’s used dumped plastic bottles and food trays to make 300,000 jeans and trucker jackets for its spring collection. Of course, not the entire product was made from plastic, but it was guaranteed that at least 20% came from recycled plastic content.
Many other items are also made from recycled plastic, some with more plastic content than others. They include bags, rugs and mats, blankets, bottles, planters, dog collars, shoes, decking, fencing, and outdoor furniture.
The Future of Plastic
While many people talk about plastic as a material that should be eradicated, it does have remarkable uses as Alan Jope implies. But there is a dire need to change our thinking. The irony is that when recycled plastic was invented it was used to try and solve environmental problems like reducing the hunting of elephants for ivory and to provide protective sheaths for electrical wiring.
There is undoubtedly too much virgin plastic being produced worldwide and during the process, there are too many other natural resources being depleted. Added to this, too many consumers have no knowledge or concern about the use and disposal of plastic products. They simply don’t care!
We, as a global nation, need to focus more on the reuse, recycling, and remanufacture of plastic, which is exactly what plastic recycling companies can do so successfully.
Ultimately, we need to eradicate plastic waste by making it useful, and there is no doubt that the mechanical engineering sector is well positioned to find solutions.
As individuals and companies alike begin to consider more sustainable building options, Passive Homes are an excellent solution. Referred to as “Passivhaus” in German, this construction concept focuses on airtight insulation to create a living space that does not require additional heating or cooling.
Developed in the 1970s, developers have incorporated the PassivHaus design in homes all over the world and in a variety of climates. As an affordable, eco-friendly and versatile construction solution, these homes will play an essential role in the future of homebuilding.
Professionals often regard eco-friendly building solutions as too expensive. While construction costs for passive homes can cost 5 to 10% more upfront than a traditional build, these fees are negligible compared to future savings. As sustainable options become standard, these costs may drop. Passive Homes rely on design principles that promote peak energy efficiency without external systems.
With a focus on proper insulation and minimizing air leakage, homeowners can save on conventional heating costs without needing to invest in expensive forms of renewable energy. While solar panels or other types of eco-friendly power are popular, because of the efficiency of the Passive House, their usage is minimal.
People build Passive Houses all over the globe in a variety of climates. The five main principles of passive homebuilding are versatile and can be altered depending on the environment. The airtight construction utilizes proper heat balance, ensuring that warm air remains inside in cooler climates, and properly ventilates in warmer ones.
Another nice feature of Passive Home construction is the ability to modify each project aesthetically. Unlike other forms of sustainable building, such as strawbale homes or shipping containers, professionals can construct Passive Homes using a variety of materials. This style does not limit builders to certain architectural styles. Because supplies can vary, many homeowners choose to add to the overall sustainability of their homes by using post-consumer building materials.
Passive Homes are eco-friendly by design. In Europe, it’s the standard building practice of the future. According to The Resolution of the European Parliament, its implementation will be mandatory in new home construction by all member states in 2021.
The elements of Passive Homes are sustainable by default and do not require relying on alternative energy systems for primary energy. The standard principles are the result of research at the Passive House Institute, and include:
Double and triple-insulated windows
Air quality management
Passive Home design principles do not rely on renewables as a primary source of energy, focusing instead on insulation and passive solar to maximize heat efficiency. They’re also the most affordable way to achieve zero-carbon, resulting in energy savings of up to 90% compared to conventional energy systems.
Passive Building for the Future
Passive Home design incorporates efficient ventilation, heat recovery and super insulation to create a high-quality structure that is not only efficient but also extremely comfortable. A contractor can adapt these buildings to any climate or design preference. While Passive Homes are already a standard — and future mandated — construction in Europe, they’re also becoming more popular in the United States.
Thanks to a U.S. Department of Energy “Building America” Grant, the PassivHaus Institute established new building standards that take into account market and climate variables throughout North America, including comfort and performance.
Any architect or contractor can easily utilize the Passive Home style, and the building standards are available via online distribution. As consumers and developers look towards a more sustainable and eco-friendly future, this style of building should be at the forefront of construction.
The increasing clamor for energy and satisfying it with a combination of conventional and renewable resources is a big challenge. Accompanying energy problems in almost all parts of the world, another problem that is assuming critical proportions is that of urban waste accumulation. The quantity of waste produced all over the world amounted to more than 12 billion tonnes in 2006, with estimates of up to 13 billion tonnes in 2011. The rapid increase in population coupled with changing lifestyle and consumption patterns is expected to result in an exponential increase in waste generation of up to 18 billion tonnes by year 2020. Ironically, most of the wastes are disposed of in open fields, along highways or burnt wantonly.
Size of the Industry
Around 130 million tonnes of municipal solid waste (MSW) are combusted annually in over 600 waste-to-energy (WTE) facilities globally that produce electricity and steam for district heating and recovered metals for recycling. The global market for biological and thermochemical waste-to-energy technologies is expected to grow to USD 29.2 billion by 2022. Incineration, with energy recovery, is the most common waste-to-energy method employed worldwide.
Since 1995, the global WTE industry increased by more than 16 million tonnes of MSW. Over the last five years, waste incineration in Europe has generated between an average of 4% to 8% of their countries’ electricity and between an average of 10% to 15% of the continent’s domestic heat.
Advanced thermal technologies, like gasification and pyrolysis, and anaerobic digestion systems are beginning to make deep inroads in the waste-to-energy sector and are expected to increase their respective market shares on account of global interest in integrated waste management framework in urban areas. Scarcity of waste disposal sites coupled with growing waste volumes and solid waste management challenges are generating high degree of interest in energy-from-waste systems among policy-makers, urban planners, entrepreneurs, utility companies etc.
Currently, the European nations are recognized as global leaders of waste-to-energy movement. They are followed behind by the Asia Pacific region and North America respectively. In 2007 there are more than 600 WTE plants in 35 different countries, including large countries such as China and small ones such as Bermuda. Some of the newest plants are located in Asia. China is witnessing a surge in waste-to-energy installations and has plans to establish 125 new waste-to-energy plants during the twelfth five-year plan ending 2015.
Incineration is the most common waste-to-energy method used worldwide.
The United States processes 14 percent of its trash in WTE plants. Denmark, on the other hand, processes more than any other country – 54 percent of its waste materials. As at the end of 2008, Europe had more than 475 WTE plants across its regions – more than any other continent in the world – that processes an average of 59 million tonnes of waste per annum. In the same year, the European WTE industry as a whole had generated revenues of approximately US$4.5bn.
Legislative shifts by European governments have seen considerable progress made in the region’s WTE industry as well as in the implementation of advanced technology and innovative recycling solutions. The most important piece of WTE legislation pertaining to the region has been the European Union’s Landfill Directive, which was officially implemented in 2001 which has resulted in the planning and commissioning of an increasing number of WTE plants over the past five years.
Food waste is a global issue that begins at home and as such, it is an ideal contender for testing out new approaches to behaviour change. The behavioural drivers that lead to food being wasted are complex and often inter-related, but predominantly centre around purchasing habits, and the way in which we store, cook, eat and celebrate food.
Consumer Behavior – A Top Priority
Consumer behaviour is a huge priority area in particular for industrialised nations – it is estimated that some western societies might be throwing away up to a third of all food purchased. The rise of cheap food and convenience culture in recent years has compounded this problem, with few incentives or disincentives in place at producer, retail or consumer level to address this.
While it is likely that a number of structural levers – such as price, regulation, enabling measures and public benefits – will need to be pulled together in a coherent way to drive progress on this agenda, at a deeper level there is a pressing argument to explore the psycho-social perspectives of behaviour change.
Individual or collective behaviours often exist within a broader cultural context of values and attitudes that are hard to measure and influence. Simple one-off actions such as freezing leftovers or buying less during a weekly food shop do not necessarily translate into daily behaviour patterns. For such motivations to have staying power, they must become instinctive acts, aligned with an immediate sense of purpose. The need to consider more broadly our behaviours and how they are implicated in such issues must not stop at individual consumers, but extend to governments, businesses and NGOs if effective strategies are to be drawn up.
Emergence of Food Waste Disposers
Food waste disposer (FWDs), devices invented and adopted as a tool of convenience may now represent a unique new front in the fight against climate change. These devices, commonplace in North America, Australia and New Zealand work by shredding household or commercial food waste into small pieces that pass through a municipal sewer system without difficulty.
The shredded food particles are then conveyed by existing wastewater infrastructure to wastewater treatment plants where they can contribute to the generation of biogas via anaerobic digestion. This displaces the need for generation of the same amount of biogas using traditional fossil fuels, thereby averting a net addition of greenhouse gases (GHG) to the atmosphere.
Food waste is an ideal contender for testing new approaches to behaviour change.
The use of anaerobic digesters is more common in the treatment of sewage sludge, as implemented in the U.K., but not as much in the treatment of food waste. In addition to this, food waste can also replace methanol (produced from fossil fuels) and citric acid used in advanced wastewater treatment processes which are generally carbon limited.
Despite an ample number of studies pointing to the evidence of positive impacts of FWDs, concerns regarding its use still exist, notably in Europe. Scotland for example has passed legislation that bans use of FWDs, stating instead that customers must segregate their waste and make it available curbside for pickup. This makes it especially difficult for the hospitality industry, to which the use of disposer is well suited. The U.S. however has seen larger scale adoption of the technology due to the big sales push it received in the 1950s and 60s. In addition to being just kitchen convenience appliances, FWDs are yet to be widely accepted as a tool for positive environmental impact.
Note: Note: This excerpt is being published with the permission of our collaborative partner Be Waste Wise. The original excerpt and its video recording can be found at this link
Biomethane is a well-known and well-proven source of clean energy, and is witnessing increasing demand worldwide, especially in European countries. Between 2012 and 2016, more than 500 biomethane production plants were built across Europe which indicates a steep rise of 165 percent. The main reasons behind the growth of biomethane industry in Europe is increasing interest in industrial waste-derived biogas sector and public interest in biogas. Another important reason has been the guaranteed access to gas grid for all biomethane suppliers.
Biomethane production in Europe has swiftly increased from 752 GWh in 2011 to 17,264 GWh in 2016 with Germany being the market leader with 195 biomethane production plants, followed by United Kingdom with 92 facilities. Biogas generation across Europe also witnessed a rapid growth of 59% during the year 2011 and 2016. In terms of plant capacities, the regional trend is to establish large-scale biomethane plants.
Sources of Biomethane in Europe
Landfill gas and AD plants (based on energy crops, agricultural residues, food waste, industrial waste and sewage sludge) are the major resources for biomethane production in Europe, with the predominant source being agricultural crops (such as maize) and dedicated energy crops (like miscanthus). In countries, like Germany, Austria and Denmark, energy crops, agricultural by-products, sewage sludge and animal manure are the major feedstock for biomethane production. On the other hand, France, UK, Spain and Italy rely more on landfill gas to generate biomethane.
A large number of biogas plants in Europe are located in agricultural areas having abundant availability of organic wastes, such as grass silage and green waste, which are cheaper than crops. Maize is the most cost-effective raw material for biomethane production. In many parts of Europe, the practice of co-digestion is practised whereby energy crops are used in combination with animal manure as a substrate. After agricultural biogas plants, sewage sludge is one of the most popular substrates for biomethane production in Europe.
Biomethane Utilization Trends in Europe
Biomethane has a wide range of applications in the clean energy sector. In Europe, the main uses of biomethane include the following:
Production of heat and/or steam
Power generation and combined heat and power production(CHP)
Replacement for natural gas (gas grid injection)
Replacement for compressed natural gas & diesel – (bio-CNG for use as transport fuel)
Replacement for liquid natural gas – (bio-LNG for use as transport fuel)
Prior to practically all utilization options, the biogas has to be dried (usually through application of a cooling/condensation step). Furthermore, elements such as hydrogen sulphide and other harmful trace elements must be removed (usually trough application of an activated carbon filter) to prevent adverse effects on downstream processing equipment (such as compressors, piping, boilers and CHP systems).
Biomethane is getting popularity as a clean vehicle fuel in Europe. For example, Germany has more than 900 CNG filling stations, with a fleet of around 100,000 gas-powered vehicles including cars, buses and trucks. Around 170 CNG filling stations in Germany sell a blend mixture of natural gas and biomethane while about 125 filling stations sell 100% biomethane from AD plants.
Barriers to Overcome
The fact that energy crops can put extra pressure on land availability for cultivation of food crops has led many European countries to initiate measures to reduce or restrict biogas production from energy crops. As far as waste-derived biomethane is concerned, most of the EU nations are phasing out landfill-based waste management systems which may lead to rapid decline in landfill gas production thus putting the onus of biomethane production largely on anaerobic digestion of food waste, sewage sludge, industrial waste and agricultural residues.
The high costs of biogas upgradation and natural gas grid connection is a major hurdle in the development of biomethane sector in Eastern European nations. The injection of biomethane is also limited by location of suitable biomethane production facilities, which should ideally be located close to the natural gas grid. Several European nations have introduced industry standards for injecting biogas into the natural gas grid but these standards differ considerably with each other.
Another important issue is the insufficient number of biomethane filling stations and biomethane-powered vehicles in Europe. A large section of the population is still not aware about the benefits of biomethane as a vehicle fuel. Strong political backing and infrastructural support will provide greater thrust to biomethane industry in Europe.
Polyvinyl chloride is one of the most widely used plastics worldwide. A major problem in the recycling of polyvinyl chloride is the high chlorine content in raw PVC and high levels of hazardous additives added to the polymer to achieve the desired material quality. As a result, PVC requires separation from other plastics before mechanical recycling. PVC products have an average lifetime of 30 years, with some reaching 50 or more years. This means that more PVC products are reaching the end-of-life and entering the waste stream, and the amount is likely to increase significantly in the near future.
PVC Recycling Methods
Currently, PVC is being recycled by either one of the two ways:
Mechanical recycling – This involves mechanically treating the waste (e.g. grinding) to reduce it into smaller particles. The resulting granules, called recyclate, can be melted and remolded into different products, usually the same product from which it came.
Feedstock recycling – Chemical processes such as pyrolysis, hydrolysis and heating are used to convert the waste into its chemical components. The resulting products – sodium chloride, calcium chloride, hydrocarbon products and heavy metals to name a few – are used to produce new PVC, as feed for other manufacturing processes or as fuel for energy recovery.
In mechanical recycling, because no chemical reaction is involved, the recyclate retains its original composition. This poses a recycling challenge because PVC products, depending on their application, contain different additives. For example, rigid PVC is unplasticized whereas flexible PVC is added plasticizers because this additive increases the plastic’s fluidity and thus, its flexibility. Even products used for the same application may still differ in composition if they have different manufacturers.
When different kinds of PVC waste are fed to a mechanical recycler, the resulting product’s composition is difficult to predict, which is problematic because most PVC products, even recycled ones, require a specific PVC content. In order to produce a high-quality recylate, the feed ideally should not be mixed with other kinds of plastic and should have a uniform material composition.Material recycling is therefore more applicable for post-industrial waste than for post-consumer waste.
Feedstock recycling is seen to be complementary to conventional mechanical recycling as it is able to treat mixed or unsorted PVC waste and recover valuable materials. However, a study showed that feedstock recycling (or at least the two that was considered) incurred higher costs than landfilling, primarily due to the low value of the recovered products. This provides little incentive for recyclers to pursue PVC recycling. This may change in the future as more stringent regulations to protect the environment are enacted. Some countries in Europe have already banned PVCs from landfills and PlasticsEurope is targeting a “zero plastic to landfill” in Europe by 2020.
Post-industrial waste is relatively pure and comes from PVC production and installation, such as cut-offs from laying of cables or scraps from the installation of window frames. These are easily recycled since they can be collected directly from processors or installers or even recycled by producers themselves as raw material to manufacture the same product.
Post-consumer waste contains mixed material and has been used for different applications. These are products that have reached the end-of-life or are replaced due to damage, like pipes from underground, window frames being replaced for renovation and electric cables recovered from demolition. These would require further sorting and cleaning, adding cost to the recycling process. The recyclate produced is usually of lower quality and consequently of decreased economic value.
Europe is leading the way for a more sustainable use of PVC with programs, such as RecoVinyl and VinylPlus, where recycling is advanced as one of the ways to use resources more efficiently and to divert as much waste as possible from landfills. Recovinyl, created in 2003, is an initiative of the European PVC industry to advance the sustainable development of the PVC industry by improving production processes, minimise emissions, develop recycling technology and boost the collection and recycling of waste.
Having been successful in all of its goals, including an increase in recycling of PVC across Europe to over 240,000 tonnes a year, in 2011 the PVC industry redefined the role of Recovinyl as part of the ambitious new ten-year VinylPlus sustainable development programme. VinylPlus works in partnership with consumers, businesses, municipalities, waste management companies, recyclers and converter, as well as the European Commission and national and local governments. The goal is to certify those companies who recycle PVC waste and those accredited converting companies who purchase recyclate to manufacture new products and applications.
Even if some types of PVC recycling are not feasible or economically viable at present, it will likely be reversed in the future as governments, manufacturers, consumers and other stakeholders create programs that innovate and find ways to achieve a sustainable future for the PVC industry.
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