Biofuels Flashcards
Describe how organic matter is converted into biogas, briefly.
Describe how vegetable oils are converted into biodiesel, briefly.
Describe how carbohydrates are converted into bioalcohols, briefly.
Organic matter is converted into fatty acids via acetogenesis. These fatty acids are then converted to biogas via methanogenesis.
Vegetable oils are converted to biodiesel via neutralisation and then Esterification.
Carbohydrates are depolymerised into mono and di- saccharides before fermentation converts them into alcohols.
How is energy fixed in biofuels, outline this process briefly.
It is fixed via photosynthesis.
Light excites a chlorophyll molecule, stating an electron transport chain through carriers such as photosystems II and I. The electron terminal acceptor is NADP^+ which becomes NADPH. Also a proton gradient is formed that pumps protons across ATP synthase, producing ATP.
What are first generation biofuels?
What is the main form in which carbohydrates are transported in the phloem?
These are made from sugars and vegetable oils found in arable crops, which can be easily extracted via conventional technology.
Sugar (sucrose) is the main form in which carbohydrates are transported in the phloem?
How is ethanol produced from sucrose crops?
What are two co-products of this process?
Sugarcane is firstly ground into feedstock, with the cane juice extracted. The cane juice is then fermented with yeast and the product which is a weak solution of ethanol (5-12%) is then distilled to produce a concentrated ethanol solution (95-99%).
Bargrasse (fibrous stalks) and CO2 (used in some beverages).
How much can 1 hectare of sugar cane produce in ethanol in 1 year?
It can produce 4000 L of ethanol in 1 year.
Describe the process of wet milling starch crops for ethanol.
For wet milling the grain is first soaked in sulphuric acid and then milled. This leaves the starch rich endosperm which is then digested with amylase to form glucose. This is then fermented with yeast to form 5-12% ethanol before distillation concentrates it to a 98% ethanol product.
Describe the process of dry milling starch crops for ethanol.
The grain is first ground and milled directly to produce seed granules. These are digested with amylase to form glucose. The glucose is then fermented to form 5-12% ethanol before distillation concentrates the product to 99.8% ethanol.
Compare both wet milling and dry milling.
There are more co products with wet milling such as corn syrup, dextrin sweeteners, gluten feed and starches. Also the process can be easily switched to produce a different product such as corn syrup.
For dry milling the plant is less complex and cheaper to build however there are less co products. One co product produced is DDG which is used in cattle feed.
How much ethanol can be produced from 1 hectare of land per year from starch crops?
1 hectare will produce 2577L of ethanol per year.
Per litre how much energy does ethanol contain compared to gasoline?
How does adding bio ethanol to gasoline benefit the gasoline?
How does the possession of oxygen in ethanol aid it?
How does using ethanol aid the environment?
Contains two thirds as much energy as gasoline.
It raises the octane rating, this reducing the chances of premature fuel combustion.
It reduces the chances if incomplete combustion and reduces the chances of CO and carcinogenic particulates being generated.
It aids the environment because the carbon within it has only been recently fixed so the CO2 produced is lessened and also it contains little sulphur so SO2 production is lessened.
What are some facts about biodiesel that can be stated?
Biodiesel production began in 2006,
Biodiesel makes up >70% of European total biofuel,
European biodiesel production accounts for 73% of the world total.
What are the main storage lipids and where are they found?
What are biodiesels?
The main storage lipids are triacylglycerols and they accumulate in sub cellular organelles called oil bodies.
Biodiesels are methyl or ethyl esters of fatty acids.
Describe the neutralisation stage in biodiesel production.
This is the first stage. The levels of fatty acids are assayed and the quantity of base required to neutralise them is determined.
Describe the transesterification process in biodiesel production.
An amount of base usually in excess of what is needed to neutralise (KOH or NaOH) is dissolved in an alcohol, methanol or ethanol. It is then reacted with the oil at a elevated temperature (50 degrees) for several hours.
After transesterification, describe the processing of the biodiesel.
The lower layer of the process is composed principally of glycerol and other waste products. The upper layer is composed of biodiesel and alcohol. This alcohol is removed via distillation or extraction with water.
