A sewer back up can be one of the costliest, messiest and most stressful problems you will ever have to deal with. It is possible that raw sewage can back up into your toilet, sink and bathtub, eventually overflowing into key areas of your house. It’s admittedly a disgusting topic to talk about, but it does happen, and it is important to know how to prevent it. So, here are a few tips on how to clear a mainline blockage:
1. Clear Roots
These are the most common culprits behind sewer backups. Roots belonging to trees and shrubs seek moisture underground and can, therefore, make their way into sewer lines through cracks in the pipe. Typically, they start small but grow and eventually obstruct the line, allowing waste to build up and back up. Here are some tips on using salt to get rid of such tree roots.
Obtain 4 pounds of rock salt and flush it down the toilet in the evening before the family goes to bed. That will give the saltwater at least 8 hours in the sewer line. For that duration, do not use any drains in the house to avoid diluting the saltwater.
After 8 hours, flush the toilet again and resume use of the drains in the house.
Follow this practice about once or twice a month. Any tree roots in the sewer line will die from the excess of sodium, and the lines will soon be clear.
2. Clear Paper Products
These include such products as paper towels, sanitary towels and diapers that are not intended for flushing. These products aren’t like toilet paper in that they do not disintegrate easily. They can, therefore, block the sewer line and cause a backup. To prevent this from happening, they should not be flushed down the toilet but should instead be thrown in the garbage.
Sanitary towels and diapers should never be flushed down the toilet as they tend to clog the sewer line the fastest. This also includes tampons. All of these should be disposed of in a specialized garbage bin placed next to the toilet, such as the ones in public restrooms.
3. Avoid Putting Grease in Drains
Grease is another culprit that has a way of causing backups. You should avoid, as much as possible, pouring grease down a drain. This also applies to cooking oil as it often has the same effect. Some people believe that using hot water to wash grease down the drain helps. That is not true. The grease will go down the drain more easily, but it will eventually cool off further down the drain and solidify. When it does that, it will clog the drain and cause a backup. The line will have a harder time letting water through and get clogged.
The best solution is to pour the grease into a container that is resistant to heat and let it cool off. You can then dispose of it in the garbage.
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.
With population of approximately 1.75 million, waste management is one of the most serious challenges confronting the local authorities. The daily solid waste generation across Gaza is more than 1300 tons which is characterized by per capita waste generation of 0.35 to 1.0 kg. Scarcity of waste disposal sites coupled with huge increase in waste generation is leading to serious environmental and human health impacts on the population.
The severity of the crisis is a direct consequence of continuing blockade by Israeli Occupation Forces and lack of financial assistance from international donor. Israeli Occupation Forces deliberately destroyed most of the sewage infrastructure in the Gaza Strip, during 2008-2009 Gaza War inflicting heavy damage to sewage pipes, water tanks, wastewater treatment plants etc.
There are three landfills in Gaza Strip – one each in southern and central part of Gaza and one in Gaza governorate. In addition, there are numerous unregulated dumpsites scattered across rural and urban areas which are not fenced, lined or monitored. Around 52% of the MSW stream is made up of organic wastes.
Domestic, industrial and medical wastes are often dumped near cities and villages or burned and disposed of in unregulated disposal sites which cause soil, air and water pollution, leading to health hazards and ecological damage. The physical damage caused to Gaza’s infrastructure by repeated Israeli aggression has been a major deterred in putting forward a workable solid waste management strategy in the Strip.
The sewage disposal problem is assuming alarming proportions. The Gaza Strip’s sewage service networks cover most areas, except for Khan Yunis and its eastern villages where only 40% of the governorate is covered. There are only three sewage water treatment stations in Gaza Strip – in Beit Lahia, Gaza city and Rafah – which are unable to cope with the increasing population growth rate. The total quantity of produced sewage water is estimated at 45 million m3 per annum, in addition to 3000 cubic meters of raw sewage sludge discharged from Gaza Strip directly into the sea every day. Sewage water discharge points are concentrated on the beaches of Gaza city, Al Shate’ refugee camp and Deir El Balah.
The continuous discharge of highly contaminated sewage water from Gaza Strip in the Mediterranean shores is causing considerable damage to marine life in the area. The beaches of Gaza City are highly polluted by raw sewage. In addition, groundwater composition in Gaza Strip is marked by high salinity and nitrate content which may be attributed to unregulated disposal of solid and liquid wastes from domestic, industrial and agricultural sources. The prevalent waste management scenario demands immediate intervention of international donors, environmental agencies and regional governments in order to prevent the situation from assuming catastrophic proportions.
Nowadays, many people are trying their best to be eco-friendly, energy saving, environmentally conscientious, and trying to lean towards a healthier lifestyle. There are many ways now to become more self-sufficient and giving the environment a break. By being self-sufficient, you’re decreasing your dependence on the environment, but using the earth’s natural resources to create your own sustainability. Being self-sufficient was originally how humankind lived for centuries, now we depend negatively on the earth’s resources, causing an imbalance and a negative impact on the earth. Whether you start small by recycling or going zero waste, some people has even attempted to create completely self-sufficient homes. Below you can find out how to start making your home more self-sufficient.
What is a self-sufficient home?
Creating a self-sufficient home doesn’t mean you need to live off the grid completely, but it means creating a home that supplies its own energy, water, food and sewage. They’re considered completely autonomous and named the ultimate green living dwellings. You can either build your own self-sufficient home, or make a few changes around your existing home; anything is doable.
Benefits of a self-sufficient home
Needless to say, establishing a self-sufficient home means you reduce your carbon footprint and energy consumption that have a negative impact on the environment. You’re also living a much more financially independent and bill-free lifestyle as you’re making your own resources. Being self-sufficient also develops and sharpens your skills, something that you can pass on to your children by allowing them to be more independent and practical.
Creating a self-sufficient home
In order to make improvements around your home to become more self-sufficient, you need to start with the simplest tasks and make your way towards the most difficult ones as you get the hang of it. Below are some ways you can start establishing a self-sufficient home:
Save a ton of energy consumption by using alternative energy methods. Switching to renewable energy like solar power may seem a little costly at first, but it’s extremely beneficial in the long run. Since you’re creating your own energy, it will save you a lot of money by not having to pay for electricity. You can start by installing solar panels called Photovoltaic (PV) on the roof, but make sure it’s in an area that gets undisrupted sunlight all year long. PV uses devices that generate electricity from saving up direct sunlight all day. You can also check the many other ways you can use solar energy through Beupp.com as they provide comprehensive information on alternative energy solutions.
Alternative heating options can be done through solar energy as well. Solar heating is capable of heating your water and saving energy. Water heating systems are achieved with a solar collector, insulated piping and a hot water storage tank. A self-sufficient home is one that provides itself with its own heat, and so you can allow your home to create heat by doing it traditionally. Install a wood burning stove as it’s an excellent way to save energy and provide warmth.
Even though you’re already getting your electricity from renewable energy like solar energy, but the use of passive lighting is another way to be self-sufficient throughout the day. You can remodel your window arrangement to design high windows and skylights to get as much sunlight throughout the day as you can. At night, use LED light bulbs that last longer, require less energy as well as not overheat your home.
Growing your own food
One of the major achievements of being self-sufficient is by growing your own organic food. Consider turning your backyard into a small greenhouse for food production or create a vegetable patch. Start small, choose your favorite herbs, fruits and vegetables and start gardening! If your home can allow it, consider having a small chicken coop for meat and egg supply as well as a cow or goat for dairy products.
Although it might seem difficult to secure an independent water supply, it’s still doable. Ideally, if you’re in a remote location, digging up a well will be highly beneficial. If not, you can go the renewable way and collect rainwater to be used for many things. Install a rainwater collecting system that leads to a filtration system to be able to drink this water, shower or use for laundry. Once this water is used once, it’s still reusable once more and that is called ‘grey water.’ Greywater is filtered once again and can be used to water your vegetable patch.
Plan for the future
Creating a self-sufficient home not only gives you the necessary skills to become practical and independent but it benefits the environment greatly. It may seem like a lot of work at first, but the rewards are more worthy. Establishing a green life will preserve the environment for future generations to come.
Do you run a marine-oriented business? If so, then you may have a unique opportunity to practice environmental conservation. Water, as you know, plays a major role in sustaining life on Earth. Anything you can do to preserve and protect water goes a long way in helping to combat climate change. Marine work covers a wide range of fields, but we found a few tips and tricks that may be applicable to most relevant businesses. Here are a few easy ways to make your marine business greener.
Use Less Chemicals in Pools
Here’s a tip for those who work in pool maintenance: use less chemicals. You can use fewer chemicals and also maintain a clean and healthy pool. This may take some strategic planning on your part, but it’s possible.
There are two main chemicals that are used to kill bacteria in pools: chlorine and bromine. Chlorine is more commonly used because it’s cheaper. But bromine is a longer-lasting chemical. Chlorine requires weekly doses because it’s neutralized quickly. You don’t need to dose the pull with bromine every week because bromine is more resilient. When you use bromine, you’re using less chemicals, which is better for the environment.
The downside to bromine is that it’s much more expensive than chlorine. If you have clients who are passionate about the environment, you could explain this to them and ask if they’d be willing to pay a slightly higher fee for bromine chemicals. Remember that you might be able to reduce the number of visits to that pool if you use bromine on it, which could reduce your operational costs.
Use Pool Covers
Water naturally evaporates from pools, and pool owners spend a lot of money having to top-off the pool with water every month. It’s a bigger problem in warmer areas, like in Nevada or Southern California. Water is a resource that’s taken for granted, and some of those aforementioned regions experience severe water shortages in times of drought. You should try and limit how often your clients’ pools are re-filled.
Convince your clients to use pool covers during months when they don’t use the pool as frequently. Covers reduce the amount of water that evaporates from the pool. You may be able to charge clients for having your employees cover and uncover the pool. You can use pathos to argue your case; pool covers also prevent young children and small animals from drowning.
Practice Eco-Friendly Boating
Do you run a business that involves boating? Be careful about which chemicals you use when you’re cleaning and maintaining your boat. Some chemicals contribute to harmful emissions, while others can pollute the ocean or lakes and kill marine life.
You should use marine foam and marine paint when you’re doing maintenance on the hull and exterior features. Those materials are eco-friendly. You should avoid using antifouling paint, which is very dangerous for marine life. You should also limit your use of household cleaners. You don’t want these chemicals spilling into the ocean. Try and use natural cleaners instead, like vinegar, lemon, and baking soda.
It’s illegal to dump sewage in any body of navigable water because sewage is bad for the ocean. Always properly dispose of sewage at a pumpout facility. Be proactive in fixing leaks, and always have absorbent towels on hand to clean oil off the bilge.
If you run a dive shop, be vigilant in protecting the reefs where you take divers. Educate divers—especially new divers—about not touching coral reefs, and about being careful where they kick their fins. Most scuba divers are respectful of the underwater ecosystems, but there’s a bad apple in every bunch. If you have to, threaten to end dives short if any diver knowingly disobeys your environmental rules.
Last, but certainly not least, recycle! Recycling is one of the easiest and most simple ways to make your marine business more eco-friendly. Regardless of whether you’re a contractor or if you work on a boat, you should always have recycling bins where you can toss used plastics and glass. Take these materials to recycling facilities so that they can be properly re-made into new items. Some recycling facilities even pay you for bringing in materials.
If you run a marine-based business, you have the potential to protect the environment in a huge number of ways. Practice eco-friendly cleaning methods and sustainability, and educate your clients on how they can contribute.
Anaerobic digestion is the natural biological process which stabilizes organic waste in the absence of air and transforms it into biofertilizer and biogas. Almost any organic material can be processed with anaerobic digestion.
Anaerobic digestion is particularly suited to wet organic material and is commonly used for effluent and sewage treatment. This includes biodegradable waste materials such as waste paper, grass clippings, leftover food, sewage and animal waste. Large quantity of waste, in both solid and liquid forms, is generated by the industrial sector like breweries, sugar mills, distilleries, food-processing industries, tanneries, and paper and pulp industries. Poultry waste has the highest per ton energy potential of electricity per ton but livestock have the greatest potential for energy generation in the agricultural sector.
Anaerobic digestion is particularly suited to wet organic material and is commonly used for effluent and sewage treatment. Almost any organic material can be processed with anaerobic digestion process. This includes biodegradable waste materials such as waste paper, grass clippings, leftover food, sewage and animal waste. The exception to this is woody wastes that are largely unaffected by digestion as most anaerobic microorganisms are unable to degrade lignin.
Anaerobic digesters can also be fed with specially grown energy crops such as silage for dedicated biogas production. A wide range of crops, especially C-4 plants, demonstrate good biogas potentials. Corn is one of the most popular co-substrate in Germany while Sudan grass is grown as an energy crop for co-digestion in Austria. Crops like maize, sunflower, grass, beets etc., are finding increasing use in agricultural digesters as co-substrates as well as single substrate.
A wide range of organic substances are anaerobically easily degradable without major pretreatment. Among these are leachates, slops, sludges, oils, fats or whey. Some wastes can form inhibiting metabolites (e.g.NH3) during anaerobic digestion which require higher dilutions with substrates like manure or sewage sludge. A number of other waste materials often require pre-treatment steps (e.g. source separated municipal organic waste, food residuals, expired food, market wastes and crop residues).
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.
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:
Wood and wood processing 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.
The Middle East region offers tremendous renewable energy potential in the form of solar, wind and bioenergy which has remained unexplored to a great extent. The major biomass producing Middle East countries are Egypt, Algeria, Yemen, Iraq, Syria and Jordan. Traditionally, biomass energy has been widely used in rural areas for domestic purposes in the Middle East. Since most of the region is arid/semi-arid, the biomass energy potential is mainly contributed by municipal solid wastes, agricultural residues and agro-industrial wastes.
Municipal solid wastes represent the best bioenergy resource in the Middle East. The high rate of population growth, urbanization and economic expansion in the region is not only accelerating consumption rates but also accelerating the generation of municipal waste. Bahrain, Saudi Arabia, UAE, Qatar and Kuwait rank in the top-ten worldwide in terms of per capita solid waste generation. The gross urban waste generation quantity from Middle East countries is estimated at more than 150 million tons annually.
In Middle East countries, huge quantity of sewage sludge is produced on daily basis which presents a serious problem due to its high treatment costs and risk to environment and human health. On an average, the rate of wastewater generation is 80-200 litres per person each day and sewage output is rising by 25 percent every year. According to estimates from the Drainage and Irrigation Department of Dubai Municipality, sewage generation in the Dubai increased from 50,000 m3 per day in 1981 to 400,000 m3 per day in 2006.
The food processing industry in Middle East produces a large number of organic residues and by-products that can be used as source of bioenergy. In recent decades, the fast-growing food and beverage processing industry has remarkably increased in importance in major countries of the Middle East.
Since the early 1990s, the increased agricultural output stimulated an increase in fruit and vegetable canning as well as juice, beverage, and oil processing in countries like Egypt, Syria, Lebanon and Saudi Arabia. There are many technologically-advanced dairy products, bakery and oil processing plants in the region.
Date palm biomass is found in large quantities across the Middle East
Agriculture plays an important role in the economies of most of the countries in the Middle East. The contribution of the agricultural sector to the overall economy varies significantly among countries in the region, ranging, for example, from about 3.2 percent in Saudi Arabia to 13.4 percent in Egypt. Cotton, dates, olives, wheat are some of the prominent crops in the Middle East
Large quantities of crop residues are produced annually in the region, and are vastly underutilised. Current farming practice is usually to plough these residues back into the soil, or they are burnt, left to decompose, or grazed by cattle. These residues could be processed into liquid fuels or thermochemically processed to produce electricity and heat in rural areas.
Energy crops, such as Jatropha, can be successfully grown in arid regions for biodiesel production. Infact, Jatropha is already grown at limited scale in some Middle East countries and tremendous potential exists for its commercial exploitation.
The Middle Eastern countries have strong animal population. The livestock sector, in particular sheep, goats and camels, plays an important role in the national economy of the Middle East countries. Many millions of live ruminants are imported into the Middle Eastern countries each year from around the world. In addition, the region has witnessed very rapid growth in the poultry sector. The biogas potential of animal manure can be harnessed both at small- and community-scale.
Biomass is a key renewable energy resource that includes plant and animal material, such as wood from forests, material left over from agricultural and forestry processes, and organic industrial, human and animal wastes. The energy contained in biomass originally came from the sun. Through photosynthesis carbon dioxide in the air is transformed into other carbon containing molecules (e.g. sugars, starches and cellulose) in plants. The chemical energy that is stored in plants and animals (animals eat plants or other animals) or in their waste is called biomass energy or bioenergy.
A quick glance at popular biomass resources
What is Biomass
Biomass comes from a variety of sources which include:
Wood from natural forests and woodlands
Agricultural residues such as straw, stover, cane trash and green agricultural wastes
Crop residues encompasses all agricultural wastes such as bagasse, straw, stem, stalk, leaves, husk, shell, peel, pulp, stubble, etc. Large quantities of crop residues are produced annually worldwide, and are vastly underutilised. Rice produces both straw and rice husks at the processing plant which can be conveniently and easily converted into energy.
Significant quantities of biomass remain in the fields in the form of cob when maize is harvested which can be converted into energy. Sugar cane harvesting leads to harvest residues in the fields while processing produces fibrous bagasse, both of which are good sources of energy. Harvesting and processing of coconuts produces quantities of shell and fibre that can be utilized.
Current farming practice is usually to plough these residues back into the soil, or they are burnt, left to decompose, or grazed by cattle. These residues could be processed into liquid fuels or thermochemically processed to produce electricity and heat. Agricultural residues are characterized by seasonal availability and have characteristics that differ from other solid fuels such as wood, charcoal, char briquette. The main differences are the high content of volatile matter and lower density and burning time.
There are a wide range of animal wastes that can be used as sources of biomass energy. The most common sources are animal and poultry manure. In the past this waste was recovered and sold as a fertilizer or simply spread onto agricultural land, but the introduction of tighter environmental controls on odour and water pollution means that some form of waste management is now required, which provides further incentives for waste-to-energy conversion.
The most attractive method of converting these organic waste materials to useful form is anaerobic digestion which gives biogas that can be used as a fuel for internal combustion engines, to generate electricity from small gas turbines, burnt directly for cooking, or for space and water heating.
Forestry residues are generated by operations such as thinning of plantations, clearing for logging roads, extracting stem-wood for pulp and timber, and natural attrition. Harvesting may occur as thinning in young stands, or cutting in older stands for timber or pulp that also yields tops and branches usable for biomass energy. Harvesting operations usually remove only 25 to 50 percent of the volume, leaving the residues available as biomass for energy.
Stands damaged by insects, disease or fire are additional sources of biomass. Forest residues normally have low density and fuel values that keep transport costs high, and so it is economical to reduce the biomass density in the forest itself.
Wood processing industries primarily include sawmilling, plywood, wood panel, furniture, building component, flooring, particle board, moulding, jointing and craft industries. Wood wastes generally are 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.
Generally, the waste from wood industries such as saw millings and plywood, veneer and others are sawdust, off-cuts, trims and shavings. 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 kg of wood in the furniture industries will lead to waste generation of almost half (45 %), i.e. 450 kg of wood. Similarly, when processing 1,000 kg of wood in sawmill, the waste will amount to more than half (52 %), i.e. 520 kg wood.
The food industry produces a large number of residues and by-products that can be used as biomass energy sources. These waste materials are generated from all sectors of the food industry with everything from meat production to confectionery producing waste that can be utilised as an energy source.
Solid wastes include peelings and scraps from fruit and vegetables, food that does not meet quality control standards, pulp and fibre from sugar and starch extraction, filter sludges and coffee grounds. These wastes are usually disposed of in landfill dumps.
Liquid wastes are generated by washing meat, fruit and vegetables, blanching fruit and vegetables, pre-cooking meats, poultry and fish, cleaning and processing operations as well as wine making.
These waste waters contain sugars, starches and other dissolved and solid organic matter. The potential exists for these industrial wastes to be anaerobically digested to produce biogas, or fermented to produce ethanol, and several commercial examples of waste-to-energy conversion already exist.
Pulp and paper industry is considered to be one of the highly polluting industries and consumes large amount of energy and water in various unit operations. The wastewater discharged by this industry is highly heterogeneous as it contains compounds from wood or other raw materials, processed chemicals as well as compound formed during processing. Black liquor can be judiciously utilized for production of biogas using anaerobic UASB technology.
Municipal Solid Wastes and Sewage
Millions of tonnes of household waste are collected each year with the vast majority disposed of in open fields. The biomass resource in MSW comprises the putrescibles, paper and plastic and averages 80% of the total MSW collected. Municipal solid waste can be converted into energy by direct combustion, or by natural anaerobic digestion in the engineered landfill.
At the landfill sites, the gas produced, known as landfill gas or LFG, by the natural decomposition of MSW (approximately 50% methane and 50% carbon dioxide) is collected from the stored material and scrubbed and cleaned before feeding into internal combustion engines or gas turbines to generate heat and power. The organic fraction of MSW can be anaerobically stabilized in a high-rate digester to obtain biogas for electricity or steam generation.
Sewage is a source of biomass energy that is very similar to the other animal wastes. Energy can be extracted from sewage using anaerobic digestion to produce biogas. The sewage sludge that remains can be incinerated or undergo pyrolysis to produce more biogas.
Food waste is one of the single largest constituent of municipal solid waste stream. In a typical landfill, food waste is one of the largest incoming waste streams and responsible for the generation of high amounts of methane. Diversion of food waste from landfills can provide significant contribution towards climate change mitigation, apart from generating revenues and creating employment 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 utilized as a single substrate in a biogas plant, or can be co-digested with organic wastes like cow manure, poultry litter, sewage, crop residues, abattoir wastes etc or can be disposed in dedicated food waste disposers (FWDs). Rising energy prices and increasing environmental concerns makes it more important to harness clean energy from food wastes.
Anaerobic Digestion of Food Wastes
Anaerobic digestion is the most important method for the treatment of food waste 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 utilization of food 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, the benefits of anaerobic digestion of food waste includes climate change mitigation, economic benefits and landfill diversion opportunities.
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.
Codigestion at Wastewater Treatment Facilities
Anaerobic digestion of sewage sludge is wastewater treatment facilities is a common practice worldwide. Food waste can be codigested with sewage sludge if there is excess capacity in the anaerobic digesters. An excess capacity at a wastewater treatment facility can occur when urban development is overestimated or when large industries leave the area.
By incorporating food waste, wastewater treatment facilities can have significant cost savings due to tipping fee for accepting the food waste and increasing energy production. Wastewater treatment plants are usually located in urban areas which make it cost-effective to transport food waste to the facility. This trend is catching up fast and such plants are already in operation in several Western countries.
The main wastewater treatment plant in East Bay Municipal Utility District (EBMUD), Oakland (California) was the first sewage treatment facility in the USA to convert post-consumer food scraps to energy via anaerobic digestion. EBMUD’s wastewater treatment plant has an excess capacity because canneries that previously resided in the Bay Area relocated resulting in the facility receiving less wastewater than estimated when it was constructed. Waste haulers collect post-consumer food waste from local restaurants and markets and take it to EBMUD where the captured methane is used as a renewable source of energy to power the treatment plant. After the digestion process, the leftover material is be composted and used as a natural fertilizer.
The first food waste anaerobic digestion plant in Britain to be built at a sewage treatment plant is the city of Bristol. The plant, located at a Wessex Water sewage works in Avonmouth, process 40,000 tonnes of food waste a year from homes, supermarkets and business across the southwest and generate enough energy to power around 3,000 homes.
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