O objetivo do meu projeto é determinar os custos de entrada e saída de energia da produção de etanol em pequena escala a partir de fontes locais e convencionais. Decidi usar beterraba açucareira orgânica cultivada localmente com equipamentos agrícolas biocombustíveis. Em comparação com os custos de uma fonte local, também usei açúcar convencional transportado do México e vendido em uma empresa local de abastecimento de restaurantes. Além disso, fiz o etanol da Amal ainda para fazer os testes.
Ethanol is a grain alcohol that can be used as fuel in most four cycle spark ignition engines. The process of making ethanol begins by extracting the sugars from a sugar crop such as sugar beets, or converting the starches of crops such as corn or potatoes to sugars. Crops used for ethanol production are titled "feed stocks". Starch and sugar crops both have their benefits depending on the region that they are produced in. The benefit of sugar crops is that they require less energy input since no starches need to be converted. The benefit of corn is that it can store much longer than sugar beets before rotting. I am using sugar beets since they were the most appropriate crop for the season and region. The sugars are extracted by juicing the beets and boiling with water. Now the solution is called "mash" and it can be fermented and then distilled to extract the ethanol. Ethanol fuel can be used in most converted engines if it has a alcohol percentage greater than 80%. Due to ethanols strong ability to bind with water, no still canremove the last 5% of water. Therefore the highest possible yield from a still is 95% ethanol. If blending ethanol with gasoline, all the water must removed to prevent separation of the gasoline and ethanol.
- 1 Process of Making Ethanol From Sugar Beets
- 2 Process of Making Ethanol From Conventional Sugar
- 3 Cost per Gallon of Ethanol
- 4 Conclusion
- 5 Project Costs
Processo de fabricação de etanol a partir de beterraba sacarina
I began by washing the beets and then slicing them up so they would fit in the juicer. I juiced 18lbs of beets which yielded 1.4gal of juice and 7.5lbs of pulp. I then added 2gal of water and mixed juice and pulp together for a total volume of 5gal.
Heated mash to 189F and held temp for 20min to kill bacteria. Total heating process took 45min. I let the mash cool to 80F and then added 100g of Turbo Yeast that was purchased online. Turbo yeast is a special strain of yeast that is claimed to produce up to 14%alc in 48hrs. When fermenting mash it is important to achieve the highest alc% possible so more alc can be collected once distilled. Once yeast was added I agitated the solution for 20min to increase yeast activation then placed on lid and air lock. I let the mash ferment for 72hrs hoping to get all sugars converted to alcohol. I was unable to determine the final alc% of my mash because the solution was too thick for an accurate hydrometer reading.
Distilling Beet Mash
The pulp which floated to the top of the fermented mash was scraped off, then the rest of the mash was transfered to the boiler of the still. The distillation began with an initial still temperature of 20.7C. After 83min of heating on a propane burner the still temperature reached 78C. Distillate began flowing out of the still and was collected at the rate of.18Liters/min. As time went on, the temperature of the still increased as alcohol was extracted from the boiler. An increase in temperature above 78.5C means more water percentage in the distillate that is being collected, and thus less overall alc% of distillate being collected. To lower the still temperature, the amount of distillate being sent back to the main column from the return line was increased by further closing the reflux valve. As the reflux valve is closed, the amount of reflux increases. The amount of reflux is determined by how much distillate is sent back to the column through the return line per amount that would flow when the reflux valve 100% is open. When more reflux is induced (more percent of distillate is sent back to the column to be re-distilled), the returned liquid drips on the top of the stainless steel scrubber pads (used as packing) and drips down, creating a temperature gradient from top to bottom. As ethanol and water vapor rise up the column from the boiler, the vapor encounters scrubber pads that cool in temperature from bottom to top. The digital thermometer used for determining still temperature is placed above the top of the stacked scrubber pads to read the temperature of the vapors passing through the scrubber pads and on to the condenser. Thus temperatures closest to 78.5C will give the highest percentage of ethanol since 78.5C is the vapor point of ethanol. As the temperature of the still increases, so does the amount of water in the vapor as it rises towards 100C (the vapor point of water). Increasing the amount of reflux drops the temperature of the still, which in turn produces a higher percent ethanol. However, when you increase the ammount of reflux, it reduces the amount of distillate being collected per minute and requires longer operation of the distillation process.
Results and Efficiencies
Total amount of distillate collected was 22oz of 80%alc. This amount became 18oz of 100% ethanol once dehydrated.Sugar beets have a sugar content around 20%, so the theoretical yield of ethanol produced is around 50%alc per weight of sugar. So one 1lb of beets with.2lb sugar should yield.1lb of ethanol. Ethanol weighs 6.5lbs/gal. So theoretically 65lb of sugar beets would yield 1gal of ethanol.
My results were that 18lbs of sugar beets yielded 18oz of ethanol. At this rate of yield it would take 128lbs to make one gallon of ethanol. My process was 50.8% efficient when compared to theoretical max yield.
- 12gal of propane were consumed to yield.14gal of ethanol. The Btu input of propane consumed was 194,192Btu to yield 10,598Btu worth of ethanol. The efficiency of ethanol produced in distillation per unit of propane used is 5.5%.
Processo de fabricação de etanol a partir de açúcar convencional
Making the Sugar Wash
The sugar mash began by boiling 4gal of water which took 62min. 25lb of conventional table sugar was added to the boiling water and the pH was lowered to 4.0. More water was added to make a final volume of 12gal. The hydrometer reading showed a Specific Gravity of 1.095 which correlates to 24% sugar and 13%alc potential. 150g of Turbo Yeast was mixed in and the wash fermented for 5 days.
Fermenting Results of Sugar Wash
After five days of fermenting, a final hydrometer reading showed that there was 1.5%alc potential left in the fermenter and that the wash was 12 gallons of 11.5%alc. 11.5% of 12gal is a theoretical maximum of 1.38gal of 100% alcohol to be distilled.
Distilling the Sugar Wash
Only 10 gallons of mash was able to fit in the still so the theoretical maximum of alcohol to be distilled lowered to 1.08gal of 100% ethanol. The still was ran for 5hrs on a propane burner and distillate was collected in three categories from start to finish (heads, mids, and tails). The heads were the first 32oz of ethanol collected which had a specific gravity of.8720 and 78%alc. The next group (mids) were collected as one gallon of 81%alc with a specific gravity of.8655. The tails were the the last 32oz collected with 54%alc and a specific gravity of.9250.
Results and Efficiencies
Total amount collected was 144.64oz (1.13gal) of 100% ethanol. My results compared to theoretical maximum yield (1.38gal 100% ethanol) are 81.9% efficient. The 5hr distillation process consumed 2.65gal of propane. 2.65gal propane multiplied by 91,600btu/gal propane is total propane Btu input of 242,740btu to make 1.13gal of ethanol. 1.13gal ethanol multiplied by 75,700btu/gal of ethanol is 98,410btu of ethanol produced.
Therefore it took 242,740btu of propane to yield 98,410btu of ethanol. The efficiency of ethanol produced in distillation per unit of propane used is 40.5%.
Custo por galão de etanol
Cost of Ethanol From Local Organic Beets
My results show that distilling with propane consumes more energy than energy stored in the ethanol produced.From this experiment, making.14gal of ethanol required 18lb of sugar beets purchased for $1.00/lb ($18.00). The mash was heated on two natural gas burners for 45min. The amount of energy used in this process is undetermined and will not be included. 100g of Turbo Yeast used cost ($4.16). The distillation process consumed 2.12gal of propane purchased for $3.00/gal ($6.36). Total cost of producing.14gal ethanol was $28.52. Therefore the cost of making ethanol from local organic sugar beets is $203.71/gal.
Cost of Ethanol Produced From Conventional Sugar
From this experiment, making 1.13gallons of ethanol required 21lb of conventional sugar purchased for $0.44/lb ($9.24). Also the wash was heated on two natural gas burners for 62min. The amount of energy consumed in this process is undetermined and will not be included in the cost of production. 150g of Turbo Yeast were used ($6.23). The distillation process consumed 2.65gal of propane purchased for $7.95. The total cost of making 1.13gal of ethanol from conventional sugar is $23.42, therefore, making one gallon of ethanol from conventional store-bought sugar costs $20.73.
A quantidade de energia colocada no etanol de beterraba local e no etanol de açúcar convencional é maior que o retorno. Os rendimentos das beterrabas açucareiras locais foram muito inferiores ao esperado, e muitos fatores poderiam estar em jogo. Misturar o suco de beterraba com a polpa pode ter prejudicado a capacidade das leveduras de se movimentar pelo mosto e fermentar todos os açúcares disponíveis. Além disso, as beterrabas utilizadas foram armazenadas por alguns meses, o que significa que sua quantidade de açúcares pode ter se degradado. Outro possível fator é que o pH não foi ajustado antes da fermentação.
O açúcar convencional teve resultados muito melhores do que a beterraba local, porém existem muitos outros custos externos já que o açúcar utilizado é um organismo modificado convencionalmente cultivado com o uso de pesticidas e fertilizantes derivados de petróleo. Deve-se questionar os insumos energéticos do cultivo dessa cultura, processamento da colheita, refino do açúcar, embalagem e envio para o norte da Califórnia do México. Todos esses fatores não puderam ser medidos no meu projeto, mas devem ser levados em consideração para sua adequação.
Este projeto começou como um experimento para fazer combustível para uma scooter. Depois de analisar os insumos energéticos da produção de etanol em pequena escala, não faz sentido fazer etanol combustível de quintal através do uso de combustíveis refinados, como gás natural e propano. No tempo que levou para produzir etanol suficiente para alimentar a scooter por 160 quilômetros, eu poderia ter percorrido a distância equivalente em minha bicicleta. O combustível de etanol só é eficiente quando as culturas são cultivadas em grande escala. A instalação de processamento para a fabricação de etanol deve ser local da cultura para reduzir os custos de transporte. O processo de trituração e destilação deve contar com recursos não fósseis. As alternativas de aquecimento são a queima de biomassa ou o possível uso de alambiques solares que concentram a energia do sol.
Custos do projeto
Custos de Ingredientes/Materiais
|40 libras de beterraba sacarina||$ 40|
|25 libras de açúcar||$ 11|
|peneira molecular zeólita de 12 libras||$ 70|
|12 onças Turbo Levedura||$ 14|
|queimador de propano||$ 48|
|tanque de propano de 5 galões||$ 24|
|Estágio||Tempo em horas|
|alambique de construção e coleta de materiais||40|
|suco de beterraba||7|