Overview of Bioenergy Technologies

A wide range of technologies are available for realizing the energy potential of biomass wastes, ranging from very simple systems for disposing of dry waste to more complex technologies capable of dealing with large amounts of industrial waste. Conversion routes for biomass wastes are generally thermo-chemical or bio-chemical, but may also include chemical and physical.

Thermal Technologies

The three principal methods of thermo-chemical conversion corresponding to each of these energy carriers are combustion in excess air, gasification in reduced air, and pyrolysis in the absence of air. Direct combustion is the best established and most commonly used technology for converting wastes to heat. During combustion, biomass is burnt in excess air to produce heat. The first stage of combustion involves the evolution of combustible vapours from wastes, which burn as flames. Steam is expanded through a conventional turbo-alternator to produce electricity. The residual material, in the form of charcoal, is burnt in a forced air supply to give more heat.

Co-firing or co-combustion of biomass wastes with coal and other fossil fuels can provide a short-term, low-risk, low-cost option for producing renewable energy while simultaneously reducing the use of fossil fuels. Co-firing involves utilizing existing power generating plants that are fired with fossil fuel (generally coal), and displacing a small proportion of the fossil fuel with renewable biomass fuels. Co-firing has the major advantage of avoiding the construction of new, dedicated, waste-to-energy power plant. An existing power station is modified to accept the waste resource and utilize it to produce a minor proportion of its electricity.

Gasification systems operate by heating biomass wastes in an environment where the solid waste breaks down to form a flammable gas. The gasification of biomass takes place in a restricted supply of air or oxygen at temperatures up to 1200–1300°C. The gas produced—synthesis gas, or syngas—can be cleaned, filtered, and then burned in a gas turbine in simple or combined-cycle mode, comparable to LFG or biogas produced from an anaerobic digester. The final fuel gas consists principally of carbon monoxide, hydrogen and methane with small amounts of higher hydrocarbons. This fuel gas may be burnt to generate heat; alternatively it may be processed and then used as fuel for gas-fired engines or gas turbines to drive generators. In smaller systems, the syngas can be fired in reciprocating engines, micro-turbines, Stirling engines, or fuel cells.

Pyrolysis is thermal decomposition occurring in the absence of oxygen. During the pyrolysis process, biomass waste is heated either in the absence of air (i.e. indirectly), or by the partial combustion of some of the waste in a restricted air or oxygen supply. This results in the thermal decomposition of the waste to form a combination of a solid char, gas, and liquid bio-oil, which can be used as a liquid fuel or upgraded and further processed to value-added products.

Biochemical Technologies

Biochemical processes, like anaerobic digestion, can also produce clean energy in the form of biogas which can be converted to power and heat using a gas engine. Anaerobic digestion is a series of chemical reactions during which organic material is decomposed through the metabolic pathways of naturally occurring microorganisms in an oxygen depleted environment. In addition, wastes can also yield liquid fuels, such as cellulosic ethanol and biodiesel, which can be used to replace petroleum-based fuels.

Anaerobic digestion is the natural biological process which stabilizes organic waste in the absence of air and transforms it into biogas and biofertilizer. Almost any organic material can be processed with anaerobic digestion. This includes biodegradable waste materials such as municipal solid waste, animal manure, poultry litter, food wastes, sewage and industrial wastes. An anaerobic digestion plant produces two outputs, biogas and digestate, both can be further processed or utilized to produce secondary outputs. Biogas can be used for producing electricity and heat, as a natural gas substitute and also a transportation fuel. Digestate can be further processed to produce liquor and a fibrous material. The fiber, which can be processed into compost, is a bulky material with low levels of nutrients and can be used as a soil conditioner or a low level fertilizer.

A variety of fuels can be produced from biomass wastes including liquid fuels, such as ethanol, methanol, biodiesel, Fischer-Tropsch diesel, and gaseous fuels, such as hydrogen and methane. The resource base for biofuel production is composed of a wide variety of forestry and agricultural resources, industrial processing residues, and municipal solid and urban wood residues. The largest potential feedstock for ethanol is lignocellulosic biomass wastes, which includes materials such as agricultural residues (corn stover, crop straws and bagasse), herbaceous crops (alfalfa, switchgrass), short rotation woody crops, forestry residues, waste paper and other wastes (municipal and industrial). The three major steps involved in cellulosic ethanol production are pretreatment, enzymatic hydrolysis, and fermentation. Biomass is pretreated to improve the accessibility of enzymes. After pretreatment, biomass undergoes enzymatic hydrolysis for conversion of polysaccharides into monomer sugars, such as glucose and xylose. Subsequently, sugars are fermented to ethanol by the use of different microorganisms. Bioethanol production from these feedstocks could be an attractive alternative for disposal of these residues. Importantly, lignocellulosic feedstocks do not interfere with food security.

Rice Straw As Bioenergy Resource

The cultivation of rice results in two types of biomass residues – straw and husk – having attractive potential in terms of energy. Rice husk, the main by-product from rice milling, accounts for roughly 22% of paddy weight, while rice straw to paddy ratio ranges from 1.0 to 4.3. Although the technology for rice husk utilization is well-established worldwide, rice straw is sparingly used as a source of renewable energy. One of the main reasons for the preferred use of husk is its easy procurement. In case of rice straw, however, its collection is difficult and its availability is limited to harvest time.

Rice straw can either be used alone or mixed with other biomass materials in direct combustion, whereby combustion boilers are used in combination with steam turbines to produce electricity and heat. The energy content of rice straw is around 14 MJ per kg at 10 percent moisture content.  The by-products are fly ash and bottom ash, which have an economic value and could be used in cement and/or brick manufacturing, construction of roads and embankments, etc.

Straw fuels have proved to be extremely difficult to burn in most combustion furnaces, especially those designed for power generation. The primary issue concerning the use of rice straw and other herbaceous biomass for power generation is fouling, slagging, and corrosion of the boiler due to alkaline and chlorine components in the ash. Europe, and in particular, Denmark, currently has the greatest experience with straw-fired power and CHP plants.

Because of the large amount of cereal grains (wheat and oats) grown in Denmark, the surplus straw plays a large role in the country’s renewable energy strategy. Technology developed includes combustion furnaces, boilers, and superheat concepts purportedly capable of operating with high alkali fuels and having handling systems which minimize fuel preparation.

A variety of methods are employed by the European plants to prepare straw for combustion. Most use automated truck unloading bridge cranes that clamp up to 12 bales at a time and stack them 4-5 bales high in covered storage. Some systems feed whole bales into the boiler. Probably the best known whole bale feeder is the “Vølund cigar feeding” concept, originally applied by Vølund (now Babcock and Wilcox-Vølund). Whole bales are pushed into the combustion chamber and the straw burned off the face of the bale.

However, the newer Danish plants have moved away from whole-bale systems to shredded straw feed for higher efficiency. For pulverized coal co-firing, the straw usually needs to be ground or cut to small sizes in order to burn completely within relatively short residence times (suspension fired systems) or to feed and mix upon injection with bed media in fluidized bed systems.

The chemical composition of feedstock has a major influence on the efficiency of biomass cogeneration. The low feedstock quality of rice straw is primarily determined by high ash content (10–17%) as compared with wheat straw (around 3%) and also high silica content in ash. On the other hand, rice straw as feedstock has the advantage of having a relatively low total alkali content, whereas wheat straw can typically have more than 25% alkali content in ash.

However, straw quality varies substantially within seasons as well as within regions. If straw is exposed to precipitation in the field, alkali and alkaline compounds are leached, improving the feedstock quality. In turn, moisture content should be less than 10% for combustion technology.

In straw combustion at high temperatures, potassium is transformed and combines with other alkali earth materials such as calcium. This in turn reacts with silicates, leading to the formation of tightly sintered structures on the grates and at the furnace wall. Alkali earths are also important in the formation of slag and deposits. This means that fuels with lower alkali content are less problematic when fired in a boiler.

Unending Benefits of Recycling Cooking Oil

Disposal of cooking oil is not an easy task. If you try to drain it, it will block your sink drains and cause you immense plumbing problems. Throwing it away is also not a good idea because it causes damage to the environment. Cooking oil cannot go to your usual recycle trash bin like other trash because the processes of recycling it are different. However, there are better ways of recycling cooking oil without harming the environment. You can have it recycled. If you are not able to do it by yourself, there are companies that offer cooking oil recycling services.

Benefits of recycling cooking oil

Recycling companies, like MBP Solutions, turn cooking oil into other products like stock feed, cosmetics and biofuel.  They also filter the oil for reuse. If you are not in any position to recycle your cooking oil, do not drain it down the sink or throw it in your waste bin. Wrap your cooking oil in a tight jar, make sure there are no spills and call the right people to come and collect it. MBP Solutions recycles both commercial and residential cooking oils.

Recycling cooking oil comes with several benefits. The technology used to recycle the oil is advanced and the final products help in both businesses and homes.

Below are some of the major benefits of recycling of cooking oil:

Renewable energy

Recycling cooking oil turns it into renewable energy used in many manufacturing firms for processing their products. One of the most notable fuels is biodiesel, which is from used oils, grease, animal fats and vegetable oils among others. Vehicles that use diesel can use this fuel effectively and businesses that use diesel-powered machines can use the fuel without any fear of harmful emissions.

Cleaner environment

We all need a clean environment and it is not what we always get. Fuels are some of the major contributor to health hazards because of emissions. Petro-diesel is very toxic as compared to biodiesel. Biodiesel is eco-friendly and does not damage a vehicle’s engine. Petro-diesel on the other hand, produces chemical compounds like sulphur that are acidic. This acid can spoil the engine. Biodiesel is a result of green technology and keeps everything safe.

Saves costs

Recycling cooking oil saves costs in many ways. At home, you can reduce your disposal costs by calling a recycling company to come for your waste oil. If you try to dispose of the oil by yourself, you may end up spending more on extra waste bins, transportation and special disposal procedures.

Companies that use recycled oil have a chance of preventing their equipment from spoiling faster than they did before the recycled oil. Maintenance costs go down and recycled oil like biodiesel is much cheaper as compared to the other kinds of imported fuels.

Creates jobs

Disposing of waste materials and recycling them is one way of creating jobs for the masses. Instead of using that money to import petro-diesel, the government uses the money to employ more people to recycle oil into more beneficial biodiesel.

Make money out of it

You can make an extra buck out of disposing your used oil. Instead of throwing your oil away, look for companies that recycle the oil and pay you for it. This will also save you on transport costs to go and dispose of your oil, because the recycling companies come to pick it up.

Wrapping it up

The most important factor about recycling is that we are working towards one goal. That goal is to maintain a greener, healthier and cleaner environment. That is our goal and recycling cooking oil is one way of doing that.

Solar Energy Prospects in Oman

Even the fleetest of glances at a map of worldwide solar energy levels shows Oman to be well placed to exploit the energy-giving rays of the sun. In fact, over the last few years, a gaggle of reports have been published extolling the virtues of exploiting this renewable energy source. However, with increasing and more urbanised populations consuming greater and greater amounts of energy, only now are governments across the Gulf and wider MENA regions seriously looking at harnessing solar power to help fill potential energy deficits.

Mr Jigar Shah, quoted in a recent article, said investors were “desperate to invest in the Middle East solar industry” and were waiting for clear instructions from the governments in the region. He said, “The economics of switching to solar energy are far better here than in South Africa, India, Brazil, China and the US. Now that the costs of developing solar technologies have significantly declined, it is time for the Middle East to turn talk into action.”

That there is huge potential in the solar industry was underlined in no uncertain terms by the announcement last year of a $2 billion project to develop solar energy power resources in Oman. The plans also envisage creating industrial plants for the manufacture of solar panels and aluminium frames, to be used by the power station and also for local consumption and export.

Knowledge and technology transfer were also critical contributors to the success of the project which also aimed to tie-up with major international technology companies and international universities with expertise in renewable energy education, to help train the local population in servicing this burgeoning industry.

David Heimhofer, Chairman of Terra Nex Group and Managing Director of Middle East Best Select Fund, said, “By attracting foreign direct investment in the growing renewable energy sector and using German expertise, Oman will become not just a regional leader in the field, but also benefit from the great intrinsic value within the complete value chain associated with this economic sector. He says“In addition to generating new jobs for the Omani people and boosting exports, this project creates an entire industry that Oman can be proud of.”

The project is expected to deliver more than 2000 jobs for Omanis across a diverse range of industrial sectors and services. In order to increase the skill set of the local population to help service these new jobs, the University of Zurich proposed the setting up of an educational institution in the Sultanate specialising in the field of renewable energy engineering.

Sugarcane Trash – A Wonderful Resource that Indian Sugar Industry is Wasting

In Indian sugar mills, the frequent cycles of ups and downs in the core business of selling sugar has led to the concentration towards the trend of ancillary businesses, like cogeneration power plant and ethanol production, becoming the profit centres. These units, which were introduced as a means to manage sugar mills’ own byproduct, like bagasse, are now keeping several sugar mills financially afloat. Thus, the concept of ‘Integrated Sugar Mill Complex’ has now become a new normal.

Limitations of Bagasse

Bagasse is a ubiquitous primary fuel in cogeneration plants in sugar mills, which adds more than 2,000 MW of renewable power to the Indian energy mix. The inclination of cogeneration plant managers towards bagasse is primarily because of its virtue of being easily available on-site, and no requirement to purchase it from the external market.

This remains true despite its several significant shortcomings as a boiler fuel, prime among which are very high moisture content and low calorific value. As a result, the fuel-to-energy ratio remains abysmally low and the consequent lesser power generation is depriving these sugar mills from achieving true revenue potential from their ancillary power business vertical, which is pegged at ~10,000 MW.

Sugarcane Trash – A Wonder Waste

Though, there is a much neglected high calorific value biomass which is available in proximity of every sugarmill and is also a residue of the sugarcane crop itself, which could enable the cogeneration units to achieve their maximum output potential. This wonder waste is sugarcane trash the dry leaves of sugarcane crop – which is left in the farms itself after sugarcane harvesting as it has no utility as fodder and generally burnt by farmers, which harms the surrounding air quality substantially.

Given its favourable properties of having very low moisture content with moderate-to-high calorific value, it could be used in most of the high pressure boiler designs in a considerable proportion along with bagasse.

cane-trash

Undeniably, sugar mills should not discontinue using bagasse as the primary fuel, but surely complement it with sugarcane trash as it would lead to an increase in their revenue generation and would also allow them to expand operations of their cogeneration plant to off-season, as using sugarcane trash with bagasse in season would leave more bagasse for off season usage.

Hurdles to Overcome

Despite these evident benefits, the major obstacle in development of sugarcane trash as an industrial boiler fuel has been its difficult collection from thousands of small and fragmented farms. Moreover, the trash becomes available and needs to be collected simultaneously during the operating season of the sugar mills, which makes deployment of resources, human or otherwise, for managing the procurement of trash very difficult for any sugar mill.

As a matter of fact, the sugar mills which initiated the pilots, or even scaled commercially, to utilise sugarcane trash along with bagasse, had to sooner or later discontinue its use, owing to the mammoth challenges discussed above.

The Way Forward

Thus, in order to utilise this wonder waste, there is a dire need to outsource its procurement to professional and organised players, like RY Energies and others, which establish the biomass supply chain infrastructure in the vicinity of the cogeneration units to make on-site availability of sugarcane trash as convenient as bagasse and enable them to procure the rich quality biomass at sustainable prices which leads to an increase in their profits.

sugarcane-trash-burning

Burning of cane trash creates pollution in sugar-producing countries

These biomass supply chain companies offer value to the farmers by processing their crop residues in timely manner, thus prevent open burning of the crop residue and contribute to a greener and cleaner environment.

Indeed, owing to its favourable fuel properties, positive environmental impact and now, with ease in its procurement, sugarcane trash biomass is the fuel of today and future for the Indian sugar mills.

Biofuels from MSW – An Introduction

Nowadays, biofuels are in high demand for transportation, industrial heating and electricity generation. Different technologies are being tested for using MSW as feedstock for producing biofuels. This article will provide brief description of biochemical and thermochemical conversion routes for the production of biofuels from municipal solid wastes.

drop-in-biofuels

Biochemical conversion

The waste is collected and milled, particles are shredded to reduce the size of 0.2-1.22 mm. MSW is pretreated to improve the accessibility of enzymes and make use of the enzymes in the bacteria for biological degradation on solid waste. The mixture of biomass is mixed with sulfuric acid and sodium hydroxide and autoclaved. After steam treatment, the mixture is filtered and washed with deionized water. The pre-treated mixture is then dried and drained overnight. The pre-treatment process improves the formation of sugars by enzymatic hydrolysis, avoids the loss of carbohydrate and avoids the formation of by-products inhibitory.

After pre-treatment (pre-hydrolysis), the mixture undergoes enzymatic hydrolysis for conversion of polysaccharides into monomer sugars, such as glucose and xylose. The common enzymes used for starch-based substrates are ?- and ?- amylase, pullulanase, isomylase and glucoamylase. Whereas for lignocellulose based substrates cellulases and ?- glucosidases.

Finally, the mixture is fermented; sugars are converted to ethanol by using microorganisms such as, bacteria, yeast or fungi. The cellulosic and starch hydrolysates ethanolic fermentation were fermented by M. indicus at 37 °C for 72 h. The fungus uses the hexoses and pentoses sugars with a high concentration of inhibitors (i.e. furfural, hydroxymethyl furfural, and acetic acid).

The composition of MSW feedstock effects the yield of the subsequent processes. A high composition of food and vegetable waste is more desirable, as these wastes are easily degradable and result in high yields compared to paper and cardboard.

Thermochemical conversion

Gasification process is carried out by treating carbon-based material with either oxygen or steam to produce a gaseous fuel which requires high temperature and pressure. It can be described as partial oxidation of the waste. At first waste is reduced in size and dried to reduce the amount of energy used in the gasifier.

Biomass_Gasification_Process

Layout of a Typical Biomass Gasification Plant

 

The carbonaceous material oxidizes (combines with oxygen) to produce syngas (carbon monoxide and hydrogen) along with carbon dioxide, methane, water vapor, char, slag, and trace gases (depending on the composition of the feedstock). The syngas is then cleaned to remove any sulfur or acid gases and trace metals (depending on the composition of the feedstock).

The main uses of syngas are direct burning on site to provide heat or energy (by using boilers, gas turbines or steam driven engines) and refined to liquid fuels such as gasoline or ethanol.

Syngas can then be converted into biofuels and chemicals via catalytic processes such as the Fischer-Tropsch process. The Fischer-Tropsch process is a series of catalytic chemical reactions that convert syngas into liquid hydrocarbons by applying heat and pressure. Hydrocracking, hydro-treating, and hydro-isomerization can also be part of the “upgrading” process to maximize quantities of different products.

Salient Features of Sugar Industry in Mauritius

Sugar industry has always occupied a prominent position in the Mauritian economy since the introduction of sugarcane around three centuries ago. Mauritius has been a world pioneer in establishing sales of bagasse-based energy to the public grid, and is currently viewed as a model for other sugarcane producing countries, especially the developing ones.

Sugar factories in Mauritius produce about 600,000 tons of sugar from around 5.8 million tons of sugarcane which is cultivated on an agricultural area of about 72,000 hectares. Of the total sugarcane production, around 35 percent is contributed by nearly 30,000 small growers. There are more than 11 sugar factories presently operating in Mauritius having crushing capacities ranging from 75 to 310 tons cane per hour.

During the sugar extraction process, about 1.8 million tons of Bagasse is produced as a by-product, or about one third of the sugarcane weight. Traditionally, 50 percent of the dry matter is harvested as cane stalk to recover the sugar with the fibrous fraction, i.e. Bagasse being burned to power the process in cogeneration plant. Most factories in Mauritius have been upgraded and now export electricity to the grid during crop season, with some using coal to extend production during the intercrop season.

Surplus electricity is generated in almost all the sugar mills. The total installed capacity within the sugar industry is 243 MW out of which 140 MW is from firm power producers. Around 1.6 – 1.8 million tons of bagasse (wet basis) is generated on an annually renewable basis and an average of around 60 kWh per ton sugarcane is generated for the grid throughout the island.

The surplus exportable electricity in Mauritian power plants has been based on a fibre content ranging from 13- 16% of sugarcane, 48% moisture content in Bagasse, process steam consumption of 350–450 kg steam per ton sugarcane and a power consumption of 27-32 kWh per ton sugarcane.

In Mauritius, the sugarcane industry is gradually increasing its competitiveness in electricity generation. It has revamped its boiler houses by installing high pressure boilers and condensing extraction steam turbine. All the power plants are privately owned, and the programme has been a landmark to show how all the stakeholders (government, corporate and small planters) can co-operate. The approach is being recommended to other sugarcane producing countries worldwide to harness the untapped renewable energy potential of biomass wastes from the sugar industry.

Where To Start On Making Your Home More Self-Sufficient

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:

Alternative energy

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.

Heating systems

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.

Lighting

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.

Water management

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 rain 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.’ Grey water 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.

Renewable Energy from Food Residuals

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 Energy Conversion 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.

Why You Should Be Investing in Solar Panels

The future is green, and it’s more important to get on board with it than ever before. The past year has seen countless climate-change related natural disasters, from the recent devastating mega-fires in California to frequent hurricanes sweeping the US and the Caribbean.

Solar panels are becoming much more accessible, for homeowners and for businesses. Traditional roof-rack solar panels can now be installed for as little as around $3,000, and are practically a no-brainer due to the energy savings you’ll make over time (you could even totally eliminate your electricity bill). Not to mention that you’ll be doing your part to help the environment in our planet’s time of need.

If you’ve always found chunky solar panels ugly and off-putting, business magnate Elon Musk has a solution. His electric car and solar panel company Tesla has recently unveiled invisible solar roof tiles. The tiles look exactly like normal roof slates, but capture the sun’s energy without drawing attention. These tiles are paving the way to normalizing sustainable, beautiful eco-homes.

To further convince you about seriously considering installing solar panels for your home, check out our list of top reasons why solar panels will benefit your household or business.

Slash Your Energy Bills

After the initial investment of purchasing the panels and installation, the energy produced is all yours. Even if you consume more energy than your panels can produce, you’ll make drastic savings on what you are currently paying by purchasing all your electricity from the grid.

You’ll make even more amazing savings if you live in a sunny state or country – prices in Brisbane, Australia, are particularly low to purchase and install solar panels. And as the city enjoys on average 261 days of sun per year, panels there will produce more than enough energy to power homes all year round.

Energy costs are only set to rise and rise – meaning that by investing in solar panels now, you’ll never feel the strain of your electricity bills going up again. This is an especially smart idea for business owners with fluctuating income, as you can more easily predict your cashflow with fixed energy prices.

Increase the Value of Your Home

If you are open to the possibility of moving to a new house in the future, you will be able to sell your current property at an increased value by equipping it with solar panels. It’s an attractive prospect for buyers if a potential home comes with very small or no electricity bills, so you’ll be making a huge return on your investment in this way, too.

Note: Be wary of ‘renting your roof’ to solar panel companies if you can’t afford to purchase the panels outright. You may want to ‘go green’ in any way you can, but buying panels is by far the most practical way to enjoy the benefits. The lengthy leases that come with rental panel contracts (often 25 years) have been seen to put off mortgage lenders. It’s highly recommended that if you want to benefit from free electricity and help the environment with solar, you should save up first to increase the value of your property – not render it unsellable.

Reduce Your Carbon Footprint

As we said, it’s never been so important to do your bit to save our eco-system. The polar ice caps are melting faster than has ever been recorded, and the earth is suffering terrible effects. As well as hurricanes and fires, we’ve also experienced floods, earthquakes and landslides all over the world this year.

Solar panels are becoming more accessible, for homeowners and businesses

In the large scheme of things, installing solar panels doesn’t seem like it will help much, but if everyone did their part to be more eco-conscious, we could significantly reduce the strain of destructive fossil fuels on the environment. By equipping your property with solar panels, you will save money while making steps to saving the environment – a tough offer to turn down!

Utilizing green energy within your business has even better rewards. Marketing your business as eco-conscious and sustainable is a great way to attract customers and impress existing ones. In recent years, studies into consumer activity have found that sustainability is a big shopping priority, especially among the millennial generation. Corporate solar panels will increase your revenue by expanding your customer base AND saving your business’s energy bills.

So – what are you waiting for? Contact a solar energy company today, who will be more than happy to assist you on your green energy journey.