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Algae Biomass Methane Digester
 

Algae Biomass Methane Digester

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Anaerobic Digestion using algae biomass to produce electricity.

Anaerobic Digestion using algae biomass to produce electricity.

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    Algae Biomass Methane Digester Algae Biomass Methane Digester Document Transcript

    • Algal Production for Biogas Electricity Methane and power produced in anaerobic digestion facilities can be utilized to replace energy derived from fossil fuels, and hence reduce emissions of greenhouse gasses. This is due to the fact that the carbon in biodegradable material such as algae is part of a carbon cycle. The carbon released into the atmosphere from the combustion of biogas has been removed by plants in order for them to grow in the recent past. This can have occurred within the last decade, but more typically within the last growing season. If the plants are re-grown, taking the carbon out of the atmosphere once more, the system will be carbon neutral. This contrasts to carbon in fossil fuels that has been sequestered in the earth for many millions of years, the combustion of which increases the overall levels of carbon dioxide in the atmosphere. Biogas plants consist of two components: a digester (or fermentation tank) and a gas holder. The digester is a cube-shaped or cylindrical waterproof container with an inlet into which the fermentable mixture is introduced in the form of a liquid slurry. The gas holder is normally an airproof steel container that, by floating like a ball on the fermentation mix, cuts off air to the digester (anaerobiosis) and collects the gas generated. In one of the most widely used designs (Figure 2), the gas holder is equipped with a gas outlet, while the digester is provided with an overflow pipe to lead the sludge out into a drainage pit. The average cost of a digester is nearly $1.5 million, and it takes about six years to earn back that original investment without any grants. Creation of biogas Biogas is a product of the metabolism of methane bacteria and is created when the bacteria degrade a mass of organic material. The methane bacteria can only work and 70CentsaGallon.com PH:941 870 2306 Email: Info@70CentsaGallon.com Skype: Biodfuel70
    • reproduce if the substrate is sufficiently bloated with water (at least 50 %). In contrast to aerobic bacteria, yeasts and fungi they cannot exist in a solid phase. Exclusion of air These micro-organisms are strongly anaerobic. If the substrate still contains oxygen, as for example is the case with liquid manure, then aerobic bacteria must use this up first. This happens during the first phase of the biogas process. Low quantities of oxygen, such as occur through the deliberate aeration of air in order to desulphurise the material, do not cause any harm. Temperature The working range of the methane bacteria lies between 0 and 70°C. At higher temperatures they are killed off, with the exception of a few strains which can survive in temperatures up to 90°C. The speed of the decomposition process is heavily dependent on temperature. The following applies: the higher the temperature, decomposition occurs more quickly, the production of gas is higher, the decomposition time is shorter and the content of methane in the biogas is lower. Practical experience has shown that there are typical temperature ranges in which particular strains of bacteria feel quite comfortable: mesophile strains at temperatures of 25-35°C thermophile strains at temperatures above 45°C The higher the temperature, the more sensitive the bacteria are to temperature variations, especially when these occur for a short time and the temperature drops. Whilst in the mesophile range daily variations of from 2 to 3°C about the medium can still be supported, for the thermophile range these variations should not be more than 1°C. Over longer periods of time (around 1 month) the bacteria become accustomed to new temperature ranges. The pH value The pH value should be in the weakly alkaline range of about 7.5. For liquid manure and dung this range usually occurs naturally during the second phase of the decomposition process, as a result of the creation of ammonium. For more acidic substrates such as slop, whey and silage it may be necessary to add lime in order to increase the pH value. Supply of nutrients Methane bacteria cannot break down fats, protein, carbohydrate (starch, sugar) and cellulose in pure form. In fact they need soluble nitrogen compounds, minerals and trace elements to break down the cellular mass of these materials. Sufficient quantities of these substances are present in dung and liquid manure. But Algae Biomass and grass too (in fresh and preserved form) as also marc, slop and whey contain sufficient total nutrients and can in principle be broken down alone. In practice however it is recommended that dung and liquid manure are used as a stable basic substrate and additional amounts of the materials referred to are added, so as to avoid segregation and to achieve a good buffering of acids and lyes. Stages 70CentsaGallon.com PH:941 870 2306 Email: Info@70CentsaGallon.com Skype: Biodfuel70
    • The key process stages of anaerobic digestion there are four key biological and chemical stages of anaerobic digestion: 1. Hydrolysis 2. Acidogenesis 3. Acetogenesis 4. Methanogenesis In most cases biomass is made up of large organic polymers. In order for the bacteria in anaerobic digesters to access the energy potential of the material, these chains must first be broken down into their smaller constituent parts. These constituent parts or monomers such as sugars are readily available by other bacteria. The process of breaking these chains and dissolving the smaller molecules into solution is called hydrolysis. Therefore hydrolysis of these high molecular weight polymeric components is the necessary first step in anaerobic digestion. Through hydrolysis the complex organic molecules are broken down into simple sugars amino acids, and fatty acids. Acetate and hydrogen produced in the first stages can be used directly by methanogens. Other molecules such as volatile fatty acids (VFA’s) with a chain length that is greater than acetate must first be catabolised into compounds that can be directly utilized by methanogens. Digestate is the solid remnants of the original input material to the digesters that the microbes cannot use. It also consists of the mineralized remains of the dead bacteria from within the digesters. Digestate can come in three forms; fibrous, liquor or a sludge- based combination of the two fractions. In two-stage systems the different forms of digestate come from different digestion tanks. In single stage digestion systems the two fractions will be combined and if desired separated by further processing. Digestate liquor can be used as a fertilizer supplying vital nutrients to soils. The solid, fibrous component of digestate can be used as a soil conditioner. The liquor can be used as a substitute for chemical fertilizers which require large amounts of energy to produce and transport. The use of manufactured fertilizers is therefore more carbon intensive than the use of anaerobic digestate fertilizer. This solid digestate can be used to boost the organic content of soils. There are some countries, such as Turkey where there are many organically depleted soils, and here the markets for the digestate can be just as important as the biogas. 70CentsaGallon.com PH:941 870 2306 Email: Info@70CentsaGallon.com Skype: Biodfuel70
    • In countries that collect household waste, the utilization of local anaerobic digestion facilities can help to reduce the amount of waste that requires transportation to centralized landfill sites or incineration facilities. This reduced burden on transportation has and will reduce carbon emissions from the collection vehicles. If localized anaerobic digestion facilities are embedded within an electrical distribution network, they can help reduce the electrical losses that are associated with transporting electricity over a national grid. The second by-product (acidogenic digestate) is a stable organic material comprised largely of lignin and cellulose, but also of a variety of mineral components in a matrix of dead bacterial cells; some plastic may be present. The material resembles domestic compost and can be used as compost or to make low grade building products such as fibreboard. The third by-product is a liquid (methanogenic digestate) that is rich in nutrients and can be used as a fertilizer dependent on the quality of the material being digested. Levels of potentially toxic elements (PTEs) should be chemically assessed. This will be dependent upon the quality of the original feedstock. In the case of most clean and source-separated biodegradable waste streams the levels of PTEs will be low. In the case of wastes originating from industry the levels of PTEs may be higher and will need to be taken into consideration when determining a suitable end use for the material. Digestate typically contains elements such as lignin that cannot be broken down by the anaerobic microorganisms. Also the digestate may contain ammonia that is phytotoxic and will hamper the growth of plants if it is used as a soil improving material. For these two reasons a maturation or composting stage may be employed after digestion. Lignin and other materials are available for degradation by aerobic microorganisms such as fungi helping reduce the overall volume of the material for transport. During this maturation the ammonia will be broken down into nitrates, improving the fertility of the material and making it more suitable as a soil improver. Large composting stages are typically used by dry anaerobic digestion technologies. 70CentsaGallon.com PH:941 870 2306 Email: Info@70CentsaGallon.com Skype: Biodfuel70
    • Wastewater The final output from anaerobic digestion systems is water. Algae Biomass Production for Biogas Algae as Biogas resource. Algae as electricity is another resource derived from algal biomass. This is not Rocket Science (here’s the layman's explanation) Algae is a single cell organism Algae feeds on the Hydrogen from the H2O and the Carbon from the CO2 and through the process of photosynthesis produces Hydrocarbon Chains and releases Oxygen. Most strains of the Green and Green-Blue Algae can double their mass every 24hour growing cycle. Different strains of Algae produce Algae Oil with slightly different hydrocarbon chains 70CentsaGallon.com PH:941 870 2306 Email: Info@70CentsaGallon.com Skype: Biodfuel70
    • Microalgae have much faster growth-rates than terrestrial crops. The per unit area yield of oil from algae is estimated to be from between 2,000 to 20,000 gallons per acre, per year(4.6 to 18.4 l/m2 per year); this is 7 to 30 times greater than the next best crop, Chinese tallow (699 gallons). Studies show that algae can produce up to 60% of their biomass in the form of oil. Because the cells grow in aqueous suspension where they have more efficient access to water, CO2 and dissolved nutrients, microalgae are capable of producing large amounts of biomass and usable oil in either high rate algal ponds or photobioreactors. This oil can then be turned into biodiesel which could be sold for use in automobiles. The biomass (algae cake) can be used for biogas production into methane to generate electricity. The more efficient this process becomes the larger the profit that is turned by the company. Regional production of microalgae and processing into biofuels will provide economic benefits to rural communities. Biobutanol Butanol can be made from algae using only a solar powered biorefinery. This fuel has an energy density similar to gasoline, and greater than that of either ethanol or methanol. In most gasoline engines, butanol can be used in place of gasoline with no modifications. In several tests, butanol consumption is similar to that of gasoline, and when blended with gasoline, provides better performance and corrosion resistance than that of ethanol. The green waste left over from the algae oil extraction can be used to produce butanol. Biogasoline Jet Fuel is being made from algae oil currently. “Flare Test”-Establish that fuel combusts, not explodes. “Can Combustor Test”-Fuel is compatible with basic jet technology. 70CentsaGallon.com PH:941 870 2306 Email: Info@70CentsaGallon.com Skype: Biodfuel70
    • Algae seems to hold the most promise to meet many needs to include methane gas production for electricity. Algae Desirable Characteristics: • Easy to grow • Grow anywhere • High yield per acre • Not used for Human or Animal Consumption • Environmentally friendly 70CentsaGallon.com PH:941 870 2306 Email: Info@70CentsaGallon.com Skype: Biodfuel70
    • Algae remove massive amounts of CO2 (Carbon dioxide) from the air. Algae farms are glutton eaters of CO2 gas providing a means for recycling waste carbon dioxide from fossil fuel combustion. It is possible to sequester as much as one billion tons of CO2 per year from algae farms. The United States has one energy plant that produces 25.3 million tons of CO2 by itself. This technology has attracted companies that need inexpensive CO2 sequestration solutions & renewable energy solutions. The combination of algae production & methane biogas is a green way to create endless renewable clean energy for many cities and industries. 70CentsaGallon.com PH:941 870 2306 Email: Info@70CentsaGallon.com Skype: Biodfuel70