Anaerobic digestion process comprises of four major steps – hydrolysis, acidogenesis, acetogenesis and methanogenesis. The biological hydrolysis is the rate limiting step and pretreatment of sludge by chemical, mechanical or thermal disintegration can improve the anaerobic digestion process. Ultrasonic disintegration is a method for breakup of microbial cells to extract intracellular material.
Ultrasound activated sludge disintegration could positively affect anaerobic digestion of sewage sludge. Due to sludge disintegration, organic compounds are transferred from the sludge solids into the aqueous phase resulting in an enhanced biodegradability. Therefore disintegration of sewage sludge is a promising method to enhance anaerobic digestion rates and lead to reduce the volume of sludge digesters.
The addition of disintegrated surplus activated sludge and/or foam to the process of sludge anaerobic digestion can lead to markedly better effects of sludge handling at wastewater treatment plants. In the case of disintegrated activated sludge and/or foam addition to the process of anaerobic digestion it is possible to achieve an even twice a higher production of biogas. Here are few examples:
STP Bad Bramstedt, Germany (4.49 MGD)
First fundamental study on pilot scale by Technical University of Hamburg-Harburg, 3 years, 1997 – 1999
reduction in digestion time from 20 to 4 days without losses in degradation efficiency
Preliminary test on pilot-scale by Technical University of Hamburg-Harburg, 6 months, 1999
increase in VS destruction of 20%
increase in biogas production of 20%
STP Bamberg, Germany (12.15 MGD)
Preliminary full-scale test, 4 months, 2002 2) Full-scale installation since June 2004
increase in VS destruction of 30%
increase in biogas production of 30%
avoided the construction of a new anaerobic digester
STP Freising, Germany (6.87 MGD)
Fundamental full-scale study by University of Armed Forces, Munich, 4 months, 2003
increase in biogas production of 15%
improved sludge dewatering of 10%
STP Meldorf, Germany (1.06 MGD)
Preliminary full-scale test, 3 months, 2004 2) Full-scale installation since December 2004
increase in VS destruction of 25%
increase in biogas production of 25%
no foam or filamentous organisms present in the anaerobic sludge digester
STP Ergolz 2, Switzerland (3.43 MGD)
Full-scale test, 3 months, 2004
increase in VS destruction of 15%
increase in biogas production of 25%
STP Beverungen, Germany (2.64 MGD)
Full-scale test, 3 months, 2004/2005
increase in VS destruction of 25%
increase in biogas production of 25%
To sum up, ultrasonication has a positive effect on sludge solubilisation, sludge volume, biogas production, flock size reduction and cells lyses. Ultrasonic pretreatment enhances the subsequent anaerobic digestion resulting in a better degradation of volatile solids and an increased production of biogas.
The use of low power ultrasound in bioreactors may present a significant improvement in cost reduction. Therefore, ultrasonic pretreatment enhances the subsequent anaerobic digestion of sewage sludge resulting in a better sludge digestion and efficient recovery of valuables.
MSW-to-Energy is the use of thermochemical and biochemical technologies to recover energy, usually in the form of electricity, steam and other fuels, from urban wastes. The main categories of MSW-to-energy technologies are physical technologies, which process waste to make it more useful as fuel; thermal technologies, which can yield heat, fuel oil, or syngas from both organic and inorganic wastes; and biological technologies, in which bacterial fermentation is used to digest organic wastes to yield fuel. These new technologies can reduce the volume of the original waste by 90%, depending upon composition and use of outputs.
Components of MSW-to-Energy Systems
Front-end MSW preprocessing
Conversion unit (reactor or anaerobic digester)
Gas cleanup and residue treatment plant
Energy recovery plant (optional)
Emissions clean up
Incineration
Combustion of raw MSW, moisture less than 50%
Sufficient amount of oxygen is required to fully oxidize the fuel
Combustion temperatures are in excess of 850oC
Waste is converted into CO2 and water concern about toxics (dioxin, furans)
Any non-combustible materials (inorganic such as metals, glass) remain as a solid, known as bottom ash (used as feedstock in cement and brick manufacturing)
Air pollution control system for fly ash, bottom ash, particulates etc.
Needs high calorific value waste to keep combustion process going, otherwise requires high energy for maintaining high temperatures
Anaerobic Digestion
Well-known biochemical technology for organic fraction of MSW and sewage sludge.
Biological conversion of biodegradable organic materials in the absence of oxygen at mesophilic or thermophilic temperatures.
Residue is stabilized organic matter that can be used as soil amendment
Digestion is used primarily to reduce quantity of sludge for disposal / reuse
Can be seen as between pyrolysis and combustion (incineration) as it involves partial oxidation.
Exothermic process (some heat is required to initialize and sustain the gasification process).
Oxygen is added but at low amounts not sufficient for full oxidation and full combustion.
Temperatures are above 650oC
Main product is syngas, typically has net calorific value of 4 to 10 MJ/Nm3
Other product is solid residue of non-combustible materials (ash) which contains low level of carbon
Pyrolysis
Thermal degradation of organic materials through use of indirect, external source of heat
Temperatures between 300 to 850oC are maintained for several seconds in the absence of oxygen.
Product is char, oil and syngas composed primarily of O2, CO, CO2, CH4 and complex hydrocarbons.
Syngas can be utilized for energy production or proportions can be condensed to produce oils and waxes
Syngas typically has net calorific value (NCV) of 10 to 20 MJ/Nm
Plasma Gasification
Use of electricity passed through graphite or carbon electrodes, with steam and/or oxygen / air injection to produce electrically conducting gas (plasma)
Temperatures are above 3000oC
Organic materials are converted to syngas composed of H2, CO
Inorganic materials are converted to solid slag
Syngas can be utilized for energy production or proportions can be condensed to produce oils and waxes
MSW-to-energy technologies can address a host of environmental issues, such as land use and pollution from landfills, and increasing reliance on fossil fuels. In many countries, the availability of landfill capacity has been steadily decreasing due to regulatory, planning and environmental permitting constraints. As a result, new approaches to waste management are rapidly being written into public and institutional policies at local, regional and national levels.
The conventional leather tanning technology is highly polluting as it produces large amounts of organic and chemical pollutants. Wastes generated by tanneries pose a major challenge to the environment. Anaerobic digestion of tannery wastes is an attractive method to recover energy from tannery wastes.
According to conservative estimates, more than 600,000 tons per year of solid waste are generated worldwide by leather industry and approximately 40–50% of the hides are lost to shavings and trimmings. Everyday a huge quantity of solid waste, including trimmings of finished leather, shaving dusts, hair, fleshing, trimming of raw hides and skins, are being produced from the industries. Chromium, sulphur, oils and noxious gas (methane, ammonia, and hydrogen sulphide) are the elements of liquid, gas and solid waste of tannery industries.
Biogas from Tannery Wastes
Anaerobic digestion (or biomethanation) systems are mature and proven processes that have the potential to convert tannery wastes into energy efficiently, and achieve the goals of pollution prevention/reduction, elimination of uncontrolled methane emissions and odour, recovery of biomass energy potential as biogas, production of stabilized residue for use as low grade fertilizer.
Anaerobic digestion of tannery wastes is an attractive method to recover energy from tannery wastes. This method degrades a substantial part of the organic matter contained in the sludge and tannery solid wastes, generating valuable biogas, contributing to alleviate the environmental problem, giving time to set-up more sustainable treatment and disposal routes. Digested solid waste is biologically stabilized and can be reused in agriculture.
Until now, biogas generation from tannery wastewater was considered that the complexity of the waste water stream originating from tanneries in combination with the presence of chroming would result in the poisoning of the process in a high loaded anaerobic reactor.
When the locally available industrial wastewater treatment plant is not provided by anaerobic digester, a large scale digestion can be planned in regions accommodating a big cluster of tanneries, if there is enough waste to make the facility economically attractive.
In this circumstance, an anaerobic co-digestion plant based on sludge and tanneries may be a recommendable option, which reduces the quantity of landfilled waste and recovers its energy potential. It can also incorporate any other domestic, industrial or agricultural wastes. Chrome-free digested tannery sludge also has a definite value as a fertilizer based on its nutrient content.
Potential Applications of Biogas
Biogas produced in anaerobic digesters consists of methane (50%–80%), carbon dioxide (20%–50%), and trace levels of other gases such as hydrogen, carbon monoxide, nitrogen, oxygen, and hydrogen sulfide. Biogas can be used for producing electricity and heat, as a natural gas substitute and also a transportation fuel. A combined heat and power plant (CHP) not only generates power but also produces heat for in-house requirements to maintain desired temperature level in the digester during cold season.
CHP systems cover a range of technologies but indicative energy outputs per m3 of biogas are approximately 1.7 kWh electricity and 2.5kWh heat. The combined production of electricity and heat is highly desirable because it displaces non-renewable energy demand elsewhere and therefore reduces the amount of carbon dioxide released into the atmosphere.
AD Plant at ECCO’s Tannery (Netherlands)
A highly advanced wastewater treatment plant and biogas system became fully operational in 2012 at ECCO’s tannery in the Netherlands. A large percentage of the waste is piped directly into the wastewater plant to be converted into biogas. This biogas digester provides a source of renewable fuel and also helps to dispose of tannery waste materials by converting waste from both the leather-making processes, and the wastewater treatment plant, into biogas. All excess organic material from the hides is also converted into biogas.
This project enables ECCO Tannery to reduce waste and to substitute virtually all of its consumption of non-renewable natural gas with renewable biogas. The aim is to use more than 40% of the total tannery waste and replace up to 60% of the total natural gas consumption with biogas.
Malaysia is gifted with conventional energy resources such as oil and gas as well as renewables like hydro, biomass and solar energy. As far as biomass resources in Malaysia are concerned, Malaysia has tremendous agricultural biomass and wood waste resources available for immediate exploitation. This energy potential of biomass resource is yet to be exploited properly in the country.
Taking into account the growing energy consumption and domestic energy supply constraints, Malaysia has set sustainable development and diversification of energy sources, as the economy’s main energy policy goals. The Five-Fuel Strategy recognises renewable energy resources as the economy’s fifth fuel after oil, coal, natural gas and hydro. Being a major agricultural commodity producer in the region Malaysia is well positioned amongst the ASEAN countries to promote the use of biomass as a source of renewable energy.
Major Biomass Resources in Malaysia
Agricultural crops e.g. sugarcane, cassava, corn
Agricultural residues e.g. rice straw, cassava rhizome, corncobs
Woody biomass e.g. fast-growing trees, wood waste from wood mill, sawdust
Malaysia is the world’s leading exporter of palm oil, exporting more than 19.9 million tonnes of palm oil in 2017. The extraction of palm oil from palm fruits results in a large quantity of waste in the form of palm kernel shells, empty fruit bunches and mesocarp fibres. In 2011, more than 80 million tons of oil palm biomass was generated across the country.
13MW biomass power plant at a palm oil mill in Sandakan, Sabah (Malaysia)
Processing crude palm oil generates a foul-smelling effluent, called Palm Oil Mill Effluent or POME, which when treated using anaerobic processes, releases biogas. Around 58 million tons of POME is produced in Malaysia annually, which has the potential to produce an estimated 15 billion m3 of biogas.
Rice Husk
Rice husk is another important agricultural biomass resource in Malaysia with very good energy potential for biomass cogeneration. An example of its attractive energy potential is biomass power plant in the state of Perlis which uses rice husk as the main source of fuel and generates 10 MW power to meet the requirements of 30,000 households.
Municipal Solid Wastes
The per capita generation of solid waste in Malaysia varies from 0.45 to 1.44kg/day depending on the economic status of an area. Malaysian solid wastes contain very high organic waste and consequently high moisture content and bulk density of above 200kg/m3. The high rate of population growth is the country has resulted in rapid increase in solid waste generation which is usually dumped in landfills.
Conclusion
Biomass resources have long been identified as sustainable source of renewable energy particularly in countries where there is abundant agricultural activities. Intensive use of biomass as renewable energy source in Malaysia could reduce dependency on fossil fuels and significant advantage lies in reduction of net carbon dioxide emissions to atmosphere leading to less greenhouse effect. However, increased competitiveness will require large-scale investment and advances in technologies for converting this biomass to energy efficiently and economically.
Wood processing industries primarily include sawmilling, plywood, wood panel, furniture, building component, flooring, particle board, moulding, jointing and craft industries. Biomass from wood processing industries is generally concentrated at the processing factories, e.g. plywood mills and sawmills. The amount of waste generated from wood processing industries varies from one type industry to another depending on the form of raw material and finished product.
Biomass from Wood Processing
The waste resulted from a wood processing is influenced by the diameter of logs being processed, type of saw, specification of product required and skill of workers. Generally, the waste from wood industries such as saw millings and plywood, veneer and others are sawdust, off-cuts, trims and shavings. Sometimes, it becomes a complex task to select the best scroll saws for wood cutting.
Sawdust arise from cutting, sizing, re-sawing, edging, while trims and shaving are the consequence of trimming and smoothing of wood. In general, processing of 1,000 kilos of wood in the furniture industries will lead to wood waste generation of almost half (45 %), i.e. 450 kilos of wood. Similarly, when processing 1,000 kilos of wood in sawmill, the waste will amount to more than half (52 %), i.e. 520 kilo of wood.
The biomass wastes generated from wood processing industries include sawdust, off-cuts and bark. Recycling of wood wastes is not done by all wood industries, particularly small to medium scale wood industries. The off-cuts and cutting are sold or being used as fuel for wood drying process. Bark and sawdust are usually burned.
Recycling of Wood Wastes
The use of wood wastes is usually practised in large and modern establishment; however, it is commonly only used to generate steam for process drying. The mechanical energy demand such as for cutting, sawing, shaving and pressing is mostly provided by diesel generating set and/or electricity grid. The electricity demand for such an industry is substantially high.
Recycling of wood wastes is not done by all wood industries, particularly by smallholders. These wastes are normally used as fuel for brick making and partly also for cooking. At medium or large establishments some of the wastes, like: dry sawdust and chips, are being used as fuel for wood drying process. Bark and waste sawdust are simply burned or dumped.
Importance of Heating Value
The heating or calorific value is a key factor when evaluating the applicability of a combustible material as a fuel. The heating value of wood and wood waste depends on the species, parts of the tree that are being used (core, bark, stem, wood, branch wood, etc.) and the moisture content of the wood. The upper limit of the heating or calorific value of 100% dry wood on a weight basis is relatively constant, around 20 MJ/kg.
In practice, the moisture content of wood during logging is about 50%. Depending on transportation and storing methods and conditions it may rise to 65% or fall to some 30% at the mill site. The moisture content of the wood waste in an industry depends on the stage where the waste is extracted and whether wood has been dried before this stage.
Biogas can be used in raw (without removal of CO2) or in upgraded form. The main function of upgrading biogas is the removal of CO2 (to increase the energy content) and H2S (to reduce risk of corrosion). After upgrading, biogas becomes biomethane and possesses identical gas quality properties as natural gas, and can thus be used as natural gas replacement. The main pathways for biomethane utilization are as follows:
Compressed natural gas (CNG) & diesel replacement – (bio-CNG for transport fuel usage)
Liquid natural gas (LNG) replacement – (bio-LNG for transport fuel usage)
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).
Although biogas is perfectly suitable to be utilized in boilers (as an environmental friendlier source for heat and steam production), this option is rather obsolete due to the abundance of alternative sources from solid waste origin.
Most Palm Oil Mills are already self-reliant with respect to heat and steam production due to the combustion of their solid waste streams (such as EFB and PKS). Consequently, conversion to electricity (by means of a CHP unit) or utilization as natural gas, CNG or LNG replacement, would be a more sensible solution.
The biogas masterplan as drafted by the Asia Pacific Biogas Alliance foresees a distribution in which 30% of the biomethane is used for power generation, 40% for grid injection and 30% as compressed/liquefied fuel for transportation purpose (Asian Pacific Biogas Alliance, 2015).
For each project, the most optimal option has to be evaluated on a case to case basis. Main decision-making factors will be local energy prices and requirements, available infrastructure (for gas and electricity), incentives and funding.
For the locations where local demand is exceeded, and no electricity or gas infrastructure is available within a reasonable distance (<5-10 km, due to investment cost and power loss), production of CNG could offer a good solution.
Moreover, during the utilization of biogas within a CHP unit only 40-50% of the energetic content of the gas is converted into electricity. The rest of the energy is transformed into heat. For those locations where an abundance of heat is available, such as Palm Oil Mills, this effectively means that 50-60% of the energetic content of the biogas is not utilized. Converting the biogas into biomethane (of gas grid or CNG quality) through upgrading, would facilitate the transportation and commercialisation of over 95% of the energetic content of the biogas.
Within the CNG utilization route, the raw biogas will be upgraded to a methane content of >96%, compressed to 250 bar and stored in racks with gas bottles. The buffered gas (bottles) will be suitable for transportation by truck or ship. For transportation over large distances (>200km), it will be advised to further reduce the gas volume by converting the gas to LNG (trough liquefaction).
Overall the effects and benefits from anaerobic digestion of POME and utilization of biomethane can be summarized as follows:
Enhanced self-sufficiency trough availability of on-site diesel replacement (CNG)
Expansion of economic activities/generation of additional revenues
Sales of surplus electricity (local or to the grid)
Sales of biomethane (injection into the natural gas grid)
Replacement of on-site diesel usage by CNG
Sales of bottled CNG
Reducing global and local environmental impact (through fuel replacement)
Reducing dependence on fossil fuel, and enhances fuel diversity and security of energy supply
Enhancement of local infrastructure and employment
Through electrical and gas supply
Through Fuel (CNG) supply
Co-Authors: H. Dekker and E.H.M. Dirkse (DMT Environmental Technology)
Note:This is the second article in the special series on ‘Sustainable Utilization of POME-based Biomethane’ by Langerak et al of DMT Environmental Technology (Holland). The first article can be viewed at this link
The concept of biomass energy is still in its infancy in most parts of the world, but nevertheless, it does have an important role to play in terms of sustainability in general and net-zero buildings in particular. Once processed, biomass is a renewable source of energy that has amazing potential. But there is a lot of work to be done to exploit even a fraction of the possibilities that would play a significant role in providing our homes and commercial buildings with renewable energy.
According to the U.S. Energy Information Administration (EIA), only about 5% of the total primary energy usage in the U.S. comes from biomass fuels. So there really is a way to go.
The Concept of Biomass Energy
Generally regarded as any carbon-based material including plants, food waste, industrial waste, reclaimed woody materials, algae, and even human and animal waste, biomass is processed to produce effective organic fuels.
The main sources of biomass include wood mills and furniture factories, landfill sites, horticultural centers, wastewater treatment plants, and areas where invasive and alien tree and grass species grow.
Whether converted into biogas or liquid biofuels, or burned as is, the biomass releases its chemical energy in the form of heat. Of course, it depends on what kind of material the biomass is. For instance, solid types including wood and suitable garbage can be burned without any need for processing. This makes up more than half the biomass fuels used in the U.S. Other types can be converted into biodiesel and ethanol.
Generally:
Biogas forms naturally in landfills when yard waste, food scraps, paper and so on decompose. It is composed mainly of carbon dioxide
Biogas can also be produced by processing animal manure and human sewage in digesters.
Biodiesel is produced from animal fats and vegetable oils including soybeans and palm oil.
Ethanol is made from various crops including sugar cane and corn that are fermented.
How Biomass Fuels Are Used
Ethanol has been used in vehicles for decades and ethanol-gasoline blends are now quite common. In fact, some racing drivers opt for high ethanol blends because they lower costs and improve quality. While the percentage of ethanol is substantially lower, it is now found in most gasoline sold in the U.S. Biodiesel can also be used in vehicles and it is also used as heating oil.
But in terms of their role in net-zero buildings:
Biomass waste is burned to heat buildings and to generate electricity.
In addition to being converted to liquid biofuels, various waste materials including some crops like sugar cane and corn can also be burned as fuel.
Garbage, in the form of yard, food, and wood waste, can be converted to biogas in landfills and anaerobic digesters. It can also be burned to generate electricity.
Human sewage and animal manure can be converted to biogas and burned as heating fuel.
Biomass as a Viable Clean Energy Source for Net-Zero Energy Buildings
Don’t rely on what I say, let’s look at some research, specifically, a study published just last year (2018) that deals with the development of net-zero energy buildings in Florida. It looked at the capacity of biomass, geothermal, hydrokinetic, hydropower, marine, solar, and wind power (in alphabetical order) to deliver renewable energy resources. More specifically, the study evaluated Florida’s potential to utilize various renewable energy resources.
Generating electricity from wind isn’t feasible in Florida because the average wind speeds are slow. The topography and hydrology requirements are inadequate and both hydrokinetic and marine energy resources are limited. But both solar and biomass offer “abundant resources” in Florida. Unlike most other renewable resources, the infrastructure and equipment required are minimal and suitable for use within building areas, and they are both compatible with the needs of net-zero energy.
The concept of net-zero buildings has, of course, been established by the World Green Building Council (GBC), which has set timelines of 2030 and 2050 respectively for new and all buildings to achieve net-zero carbon goals. Simplistically, what this means is that buildings, including our homes, will need to become carbon neutral, using only as much renewable energy as they can produce on site.
But nothing is simplistic when it comes to net-zero energy buildings (ZEB) ). Rather, different categories offer different boundaries in terms of how renewable energy strategies are utilized. These show that net-zero energy buildings are not all the same:
ZEB A buildings utilize strategies within the building footprint
ZEB B within the site of the property
ZEB C within the site but from off-site resources
ZEB D generate renewable energy off-site
While solar works for ZEB A and both solar and wind work for ZEB B buildings, biomass and biofuels are suitable for ZEB C and D buildings, particularly in Florida.
Even though this particular study is Florida-specific, it indicates the probability that the role of biomass energy will ultimately be limited, but that it can certainly help buildings reach a net-zero status.
There will be different requirements and benefits in different areas, but certainly professionals offering engineering solutions in Chicago, New York, London (Canada and the UK), and all the other large cities in the world will be in a position to advise whether it is feasible to use biomass rather than other forms of eco-friendly energy for specific buildings.
Biomass might offer a more powerful solution than many people imagine.
Municipal waste management in Poland has changed dramatically since the early ’90s when, as part of Poland’s privatisation program, municipal authorities were freed of their waste management obligations. The combined Polish recycling rate for dry recyclables and organic waste has increased from 5% in 2004 to 21% in 2010, according to a Copenhagen Resource Institute (CRI) study Municipal Waste Management in Poland (2013). Another source provides similar, corroborating statistics, putting the dry recycling rate in Poland at 14% and the composting rate at 7%.
The latest Eurostat data (for 2011) shows that the upward trend continuing, with the total recycled and composted reaching 28%. That is rapid rate of improvement, but leaves Poland well below the latest EU-27 average of 40% (25% recycled and 15% composted) – so what prospect is there of Poland reaching the EU’s mandatory 50% target by 2020?
Responsibility for waste disposal shifted to householders, who were left to individually contract any waste collection company of their choice. In the hard economic climate a ‘cheaper-the-better’ mentality prevailed, which did little to encourage sustainable practices. There wasn’t even an obligation on householders even to sign up for waste collection.
Landfilling was – and remains – the most common way of handling waste, but accompanying reporting and tracking methods were inadequate. Statistically, quantities of waste produced were usually larger than those collected, with the missing tonnages usually being dumped in forests or burned in domestic boilers to avoid waste disposal costs. As a result, waste management became largely uncontrolled, with a 2011 report concluding that ‘’waste management is one of the most badly neglected and at the same time one of the most urgent environmental issues for Poland.’’
Waste Management Legislation
Even after joining the EU in 2005, Poland didn’t rush to introduce reforms to improve practices and help to meet recycling targets. Only recently has Poland introduced several pieces of new waste related legislation, including:
Act on maintaining cleanliness and order in municipalities (2012);
Act on Waste (2012); and
Act on management of packaging and packaging waste (2013).
The first of these was revolutionary in that it gave responsibility for municipal waste collection and disposal back to municipalities. Now they are required to organise garbage collection and the separate collection of biodegradable waste and recyclable materials such as paper, metal, glass and plastic. It is expected that the new law will improve waste management control measures on a local level and greatly reduce the illegal dumping and trash burning.
The Act on Waste helps tackle the previous ‘free for all’ amongst collectors – it obliges waste handlers to act in a manner consistent with waste management principles and plans adopted at national level (by the Council of Ministers), regional level (Voivodeship) and local level (Municipality).
Poland has also this year adopted a new National Waste Management Plan, which states that an essential step towards improving the recycling rate in Poland is to increase landfill fees for recyclable, compostable or recoverable material. If acted upon, this could greatly increase the incentive to divert important municipal waste streams from landfill. The Polish market is clearly responsive to cost: in 2008 after landfill tax was significantly raised, there was a substantial reduction in waste being landfilled.
Declaration of bin-dependence
Although Polish citizens have always had to pay directly for waste collection, the new legislation has made some substantial changes to the payment system. There are now three different calculation methods. Each household is subject to a standard fee, which is then adjusted to reflect either:
The number of people living in a household;
The number of square metres covered by the property; or
The number of cubic metres of water used by the household per month.
The first of these options seems to be the most reasonable and has proven the most popular.
Municipalities are left to determine the standard collection fee, which as a result varies from region to region. Some municipalities charge at little as 3 Polish Zloty (around £0.56) per household, per person, per month, while some charge 20 Zloty (around £3.75).
The standard charge is also affected by a declaration made by the householder regarding waste segregation. If a property owner declares that they have separated out recyclable materials then they pay considerably lower fees. In some municipalities, this could be as low as 50% of the usual charge. Only those who declare that they don’t want to recycle pay full price. It’s rare that people do so: who would pick the most expensive option?
The problem is that some householders declare that they recycle their waste while in reality they don’t. Unfortunately, abusing the system is easy to get away with, especially since the new scheme is still in its early stages and is not yet stable. Monitoring recycling participation in order to crack down on such abuses of the system represents quite a challenging task.
Future Perspectives
Transformation periods are always hard and it is common that they bring misunderstanding and chaos. It isn’t surprising that there are problems with the new system which require ironing out, and the new legislation is nevertheless welcome. However, there is still much work to be done to provide sufficient and sustainable waste management in Poland. This will include such measures as educating the population, improving waste separation at source and securing waste treatment capacity.
Perhaps most importantly, Poland needs to take immediate action to develop its municipal waste treatment capacity across the board. If the 2020 recycling target is to be met, the country will require material recovery facilities, anaerobic digestion and in vessel composting sites, and household waste and recycling centres; and if more waste is to be diverted from landfill it will also need energy from waste (EfW) incinerators and mechanical biological treatment facilities.
According to Eurostat, only 1% of waste in Poland was incinerated in 2011. It has been confirmed so far that an EfW plant will be developed in each of Poland’s 11 biggest cities. Fortunately for Poland, the development of waste treatment installations is quite generously funded by the EU, which covers up to 80% of the total cost: EU subsidy agreements have already been signed for three of the planned EfW plants. The remaining cost will be covered by central, regional and local government.
The CRI paper presents three different scenarios for the future recycling rate in Poland. One of them is very optimistic and predicts that Poland has a chance to meet the 2020 recycling requirements, but each is based simply on a regression analysis of recent trends, rather than an analysis of the likely impact of recent and planned policy measures. What it does make clear, though, is that if Poland continues to progress as it has since 2006, it will reach the 2020 target. How many EU countries can claim that?
Note: The article is being republished with the kind permission of our collaborative partner Isonomia. The original version of the article can be found at this link.
A palm oil plantation yields huge amount of biomass wastes in the form of empty fruit bunches (EFB), palm oil mill effluent (POME) and palm kernel shell (PKS). In a typical palm oil mill, empty fruit bunches are available in abundance as fibrous material of purely biological origin. Energy potential of empty fruit bunches is attractive as it contains neither chemical nor mineral additives, and depending on proper handling operations at the mill, it is free from foreign elements such as gravel, nails, wood residues, waste etc.
However, EFB is saturated with water due to the biological growth combined with the steam sterilization at the mill. Since the moisture content in EFB is around 67%, pre-processing is necessary before EFB can be considered as a good fuel.
Unprocessed EFB is available as very wet whole empty fruit bunches each weighing several kilograms while processed EFB is a fibrous material with fiber length of 10-20 cm and reduced moisture content of 30-50%. Additional processing steps can reduce fiber length to around 5 cm and the material can also be processed into bales, pellets or pulverized form after drying.
There is a large potential of transforming EFB into renewable energy resource that could meet the existing energy demand of palm oil mills or other industries as well as to promote sustainability in the palm oil industry. Pre-treatment steps such as shredding/chipping and dewatering (screw pressing or drying) are necessary in order to improve the fuel property of EFB.
Pre-processing of EFB will greatly improve its handling properties and reduce the transportation cost to the end user i.e. power plant. Under such scenario, kernel shells and mesocarp fibres which are currently utilized for providing heat for mills can be relieved for other uses off-site with higher economic returns for palm oil millers.
The fuel could either be prepared by the mills before sell to the power plants, or handled by the end users based on their own requirements. Besides, centralized EFB collection and pre-processing system could be considered as a component in EFB supply chain. It is evident that the mapping of available EFB resources would be useful for EFB resource supply chain improvement. This is particular important as there are many different competitive usages. With proper mapping, assessment of better logistics and EFB resource planning can lead to better cost effectiveness for both supplier and user of the EFB.
A covered yard is necessary to store and supply a constant amount of this biomass resource to the energy sector. Storage time should however be short, e.g. 5 days, as the product; even with 45% moisture is vulnerable to natural decay through fungi or bacterial processes. This gives handling and health problems due to fungi spores, but it also contributes through a loss of dry matter trough biological degradation. Transportation of EFB is recommended in open trucks with high sides which can be capable of carrying an acceptable tonnage of this low-density biomass waste.
For EFB utilization in power stations, the supply chain is characterized by size reduction, drying and pressing into bales. This may result in significantly higher processing costs but transport costs are reduced. For use in co-firing in power plants this would be the best solution, as equipment for fuel handling in the power plant could operate with very high reliability having eliminated all problems associated with the handling of a moist, fibrous fuel in bulk.
Pyrolysis of scrap tires offers an environmentally and economically attractive method for transforming waste tires into useful products, heat and electrical energy. Pyrolysis refers to the thermal decomposition of scrap tires either in the absence or lack of oxygen. The principal feedstocks for pyrolysis are pre-treated car, bus or truck tire chips. Scrap tires are an excellent fuel because of their high calorific value which is comparable to that of coal and crude oil. The heating value of an average size passenger tire is between 30 – 34MJ/kg.
Pyrolysis is the most recommended alternative for the thermochemical treatment of waste tires and extensively used for conversion of carbonaceous materials in Europe and the Asia-Pacific. Pyrolysis is a two-phase treatment which uses thermal decomposition to heat the rubber in the absence of oxygen to break it into its constituent parts, e.g., pyrolysis oil (or bio oil), synthetic gas and char. Cracking and post-cracking take place progressively as the material is heated to 450-500°C and above.
Process Description
The pyrolysis method for scrap tires recycling involves heating whole or halved or shredded tires in a reactor containing an oxygen free atmosphere and a heat source. In the reactor, the rubber is softened after which the rubber polymers disintegrate into smaller molecules which eventually vaporize and exit from the reactor. These vapors can be burned directly to produce power or condensed into an oily type liquid, called pyrolysis oil or bio oil.
Some molecules are too small to condense and remain as a gas which can be burned as fuel. The minerals that were part of the tire, about 40% by weight, are removed as a solid. When performed well a tire pyrolysis process is a very clean operation and has nearly no emissions or waste.
The heating rate of tire is an important parameter affecting the reaction time, product yield, product quality and energy requirement of the waste tire pyrolysis process. If the temperature is maintained at around 450oC the main product is liquid which could be a mixture of hydrocarbon depending on the initial composition of waste material. At temperature above 700oC, synthetic gas (also known as syngas), a mixture of hydrogen and carbon monoxide, becomes the primary product due to further cracking of the liquids.
Schematic for Pyrolysis of Scrap Tires
The nature of the feedstock and process conditions defines the properties of the gas, liquid and solid products. For example, whole tires contain fibers and steel while shredded tires have most of the steel and sometimes most of the fiber removed.
Processes can be either batch or continuous. The energy required for thermal decomposition of the scrap tires can be in the form of directly-fired fuel, electrical induction and or by microwaves (like a microwave oven). A catalyst may also be required to accelerate the pyrolysis process.
Useful Products
The high acceptance of pyrolysis for the treatment of scrap tires is due to the fact that the derived oils and syngas can be used as biofuels or as feedstock for refining crude oil or chemical products. The pyrolysis oil (or bio oil) has higher calorific value, low ash, low residual carbon and low sulphur content.
The use of pyrolysis oil in cement kilns, paper mills, power plants, industrial furnaces, foundries and other industries is one of the best uses of scrap tires. Pyrolysis of scrap tyres produces oil that can be used as liquid fuels for industrial furnaces, foundries and boilers in power plants due to their higher calorific value, low ash, residual carbon and sulphur content.
The solid residue, called char, contains carbon black, and inorganic matter. It contains carbon black and the mineral matter initially present in the tire. This solid char may be used as reinforcement in the rubber industry, as activated carbon or as smokeless fuel.
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