There are two types of ethanol production suitable for Canadian conditions: conventional grain-based ethanol and cellulosic ethanol. The difference between them lies not in the final product, but in the feedstock the fuel is made from and the processes used to produce it. Grain based ethanol is made from starchy feedstocks such as corn, wheat and barley, while cellulosic ethanol can be made from any non-food portion of a plant, ideally those that are high in cellulose (a polysaccharide that is the primary cell wall component of most green plants). The most common renewable feedstocks identified for cellulosic ethanol production include cereal straws and corn stover or dedicated energy grasses such as switchgrass.

Conventional ethanol is an alcohol with a production process similar to brewing beer, where starch crops like wheat and corn are converted into sugars. The sugars are fermented into ethanol, which is then distilled into its final form. This process of transforming starch-rich natural material into ethanol is called hydrolysis. Conventional ethanol production involves either wet or dry milling. Wet milling is only used for corn since it has a higher moisture content at harvest than barley and wheat. Both processes result in different by-products. Dry milling produces Distillers Dried Grain with Solubles (DDGS), a high quality and nutritious livestock feed. Wet milling produces corn oil, corn gluten meal (CGM) and corn gluten feed (CGF).

As with grains, processing cellulosic biomass aims to extract fermentable sugars from feedstocks. Two processing options are employed to produce fermentable sugars from cellulosic biomass. One approach utilizes acid hydrolysis to break down the complex carbohydrates into simple sugars. An alternative method, enzymatic hydrolysis, utilizes enzymes to convert the cellulosic biomass to fermentable sugars. The final step involves fermentation, yielding ethanol and carbon dioxide.

Energy feedstocks for ethanol production

Corn is currently the most important feedstock for ethanol production in both Canada and the US. With the expansion of ethanol production in western Canada, wheat is becoming another important feedstock. Lower grades of wheat can be utilized that do not meet typical standards for milling. It can be expected, however that as Canada’s ethanol industry continues to grow and if market prices for wheat for human consumption decline, farmers will show increasing interest in higher yielding wheat varieties for the ethanol market.

Cellulosic ethanol
Where conventional ethanol mostly makes use of the grain by converting the starch sugars from the feedstock, cellulosic ethanol uses a much larger portion of the plant, specifically a compound contained mostly in the plant cell walls and structure. This compound called cellulose, a polysaccharide or sugar, is then converted into simple sugars and fermented into ethanol. The hemi-cellulose components of plants can also be converted into ethanol but at a lower efficiency than the cellulosic component of plants. The lignin component of the plant, which is a by-product of cellulosic ethanol processing, is used as a source of energy to produce heat and electricity for cellulosic ethanol facilities and minimizes the amount of fossil fuels required for ethanol production. Both crop residues and energy crops can be used for making cellulosic ethanol. In particular, wheat, barley and oat straw are promising feedstocks for advancing the industry in western Canada.

Switchgrass
Switchgrass has one of the highest potentials as a biofuel crop in North America because it grows well under a wide range of conditions. Switchgrass is resistant to many pests and plant diseases and is capable of producing high yields with very low fertilizer applications. This means that the need for chemical inputs is relatively low. Switchgrass can be grown on marginal crop lands where other crops have caused soil degradation, or where weather conditions are too variable for reliable production of other crops.  Switchgrass was a dominant grass on the North America prairie that originally built some of the most productive and rich topsoil in the western Hemisphere. It improves soil aggregate stability and increases soil organic matter levels.  It has a significant root mass which provides large underground biomass storage of carbon, thereby acting as a sink for carbon to help offset greenhouse gas emissions.

Switchgrass has a productive stand life of 10 years or more. It can be easily rotated with regular farm crops and can be grazed or hayed to supplement forage production on livestock farms. It can be grown and harvested with equipment that most farms already possess and is harvested in early fall when haying equipment is generally not in use. Switchgrass has lower nitrogen, ash and lignin content than other herbaceous species. Ethanol yield estimates from switchgrass are 330 litres per tonne. With an average switchgrass yield of 10 tonnes per hectare, one hectare can produce 3300 litres of ethanol, equivalent to 69 GJ/ha of energy. The major advantage of switchgrass is that it produces approximately the same ethanol yield per hectare as corn, but on marginal farmland with fewer production inputs. Higher ethanol yields per tonne may be achieved in the future as this process continues to be developed.

Switchgrass cellulosic ethanol yields
Net Yield (t/ha)	Ethanol Produced (L/t)	Ethanol Yield (L/ha)	Energy Conversion (GJ/L)	Gross Energy (GJ/ha)
10.0	330	3300	0.021	69

Economics of ethanol

The prospects for the ethanol industry in Canada improved substantially after the federal government pledged financial support of $100CAD million for the sector under the framework of its Kyoto commitments. Under the plan, E-10 blends are to achieve a 35% market penetration by 2010, increasing Canada's ethanol production to about 2.74 billion litres. Current ethanol production in Canada is estimated at 0.60 billion litres from about 1 million tonnes of corn and 500,000 tonnes of wheat. Once the new Greenfield Ethanol and Husky Energy plants are fully operational in 2007, total ethanol production in Canada is expected to be near 0.84 billion litres. Assuming present Canadian gasoline consumption is about 33-35 billion litres annually, this total production would represent 2.5% of Canada’s total transportation fuel requirements. In contrast to the limited amounts of grain ethanol, cellulosic ethanol produced from switchgrass, mixed prairie grasses and woody plants grown on marginal land could potentially meet a portion of the growing demand for fuel. There may even be some added economic benefits from developing the cellulosic ethanol market, in particular, increasing employment for rural communities.

Production costs of ethanol feedstocks   Total Costs ($/hectare) Corn1 $1260 Wheat2 $467 Barley2 $451 Ontario corn, 2005 2 Manitoba Agriculture, Food and Rural Initiatives, 2004

An economic comparison between the different crops used to produce ethanol is difficult because they are grown in different regions of the country with different soil and climate characteristics. As such, the regional case studies below examining the costs and benefits for producing conventional corn ethanol using dry and wet milling are done separately for each feedstock. They include the cost of production of the feedstocks and ethanol with the general revenues that can be expected. Local crop production incentives have not been included due to regional variability. The process costs are given in a range because these depend on the scale and type of milling process used. The initial investment for wet milling is higher, but there is no energy usage for drying. In the case of very large corn ethanol processing plants, the economics of production often favour the wet milling process because no energy is used for drying, despite a lower conversion rate. Again, the economic advantage between dry milling and wet milling for corn depends on the production scale, operating costs and by-product prices.

The processing costs are made up of variable operating expenses which include electricity, fuels, waste management, water, enzymes, yeast, chemicals, denaturant, maintenance, labour, administrative costs, etc. Variable cost components vary widely between different ethanol producing plants. For instance, electricity and natural gas price differ per region, as well as the total energy used by ethanol plants and their labour and maintenance costs. Some cost components showed less variation across different ethanol plants. Enzymes, yeast, denaturant, and chemical costs are nearly constant. Larger plants generally incur lower expenses per litre of ethanol for labour and maintenance however. The processing costs documented in these case studies range from $0.11–0.14 per litre.

Although not included in these case studies, cellulosic ethanol seems to be a promising opportunity for the future because it can be produced from a wide variety of lower cost biomass feedstocks including agricultural plant residues (e.g. corn stover and cereal straws), those from industrial processes (e.g. sawdust and paper pulp) and energy crops such as switchgrass grown specifically for fuel production. Cellulosic ethanol appears to have significant potential for cost reduction compared to grain based ethanol systems because of lower feedstock costs. However, the actual costs of producing cellulosic ethanol are not yet adequately understood, as construction of a large scale cellulosic ethanol plant has not been completed or operated to date. The current value of ethanol is $0.51 per litre (July 2007) and the current incentive for ethanol (in Ontario) is approximately 16 cents/L (10¢ federal + 6¢ provincial). The value of DDGS is about $135 per tonne (July 2007) and the values of the wet milling by-products are about $125, $470 and $45 per tonne for corn oil, corn gluten meal and corn gluten feed respectively (July 2007). Alternately, grain corn can be sold at $145/tonne (Agriculture and Agri-Food Canada 2007).

Influence of choice of feedstocks on ethanol feedstock costs per litre   price  per tonne litres per tonne Raw feedstock costs per litre Corn1 145 4001 0.36 Wheat2 210 3601 0.58 Barley2 165 3651 0.45 Switchgrass 50-803 3302 0.15-0.24 1 Kim et al, 2004 2 United States Department of Energy, 2007 3 REAP-Canada estimates

 

CASE STUDY 1: Ethanol Production from Corn in Ontario
		Yield	Price	Expenses and Revenues
		Dry (D)/ Wet (W)		Unprocessed	Processed
					Dry Milling	Wet Milling
		(unit/ha)	($/unit)	($/ha)	($/ha)	($/ha)
Expenses	Feedstock production			1260	1260	1260
	Ethanol production			---	370-470	351-447
Revenues	Corn	8.4 t	145	1218	---	---
	Ethanol	3360L (D)/ 3190L (W)	0.51	---	1714	1627
	DDGS	2473 kg (D)	0.135	---	334	---
	Corn oil	305 kg (W)	0.125	---	---	38
	Corn Gluten Meal	376 kg (W)	0.47	---	---	177
	Corn Gluten Feed	1597 kg (W)	0.045	---	---	72
Net Revenues	(excl. incentives)		-42	318-418	207-303
	(incl. incentives)		0.16	---	856-956	717-813

 

CASE STUDY 2: Ethanol Production from Wheat in Western Canada
		Yield	Price	Expenses and Revenues
				Unprocessed	Processed
		(unit/ha)	($/unit)	($/ha)	($/ha)
Expenses	Feedstock production			467	467
	Ethanol production			---	111-141
Revenues	Wheat	3.0 t	210	630
	Ethanol	1080 L	0.51	---	551
	DDGS	795 kg	0.315	---	107
Net Revenues	(excl. incentives)			163	50-80
	(incl. incentives)*		0.16	---	223-253

* assumed that the provincial incentive of 6 cents is also provided by the western provinces.

CASE STUDY 3: Ethanol Production from Barley in Western Canada
		Yield	Price	Expenses and Revenues
				Unprocessed	Processed
		(unit/ha)	($/unit)	($/ha)	($/ha)
Expenses	Feedstock production			451	451
	Ethanol production			---	152-193
Revenues	Barley	3.0 t	165	495	---
	Ethanol	1095 L	0.51	---	558
	DDGS	806 kg	0.315	---	109
Net Revenues	(excl. incentives)			44	23-64
	(incl. incentives)*		0.16	---	198-239

* assumed that the provincial incentive of 6 cents is also provided by the western provinces.

Environmental impacts associated with ethanol production and use

Agricultural Sustainability
The cultivation of annual crops such as corn and cereal grains can cause soil erosion and often require high amounts of production inputs. It is important to grow these crops in rotation as intensive cropping leads to soil compaction, soil nutrient and organic matter depletion, and decreased crop yields. Maintenance of soil organic matter is essential. The use of conservation tillage and the return of crop residues to the soil will help maintain soil sustainability, hence the long-term productive capacity of these soils to grow feedstocks. Leaving approximately 1 t/ha of straw coverage has been estimated to ensure soil erosion protection for annual grain crops in western Canada, although this rate can vary greatly depending on crop and soil type and tillage regimes. The amounts required to maintain long-term soil fertility are higher than this recommendation, but are again region and soil specific.

Growing native warm season grasses on a large scale can significantly improve the sustainability of agriculture and soil, reducing both erosion and pesticide use by approximately 90% and protecting organic matter and topsoil. Perennial grasses such as switchgrass are especially beneficial because no soil disturbance occurs and there is approximately 25% turnover of the root mass per year. The deep root system of the crop helps to maintain and increase soil organic matter, especially when compared with conventional field crops. Also, they tend not to lose nutrients as easily from soils as annual crops. Warm season grasses can reduce runoff coming from agricultural watersheds by 87% and sediment loss by up to 93%. In addition, established perennial energy crops require less fertilizers and pesticides than conventional row crops, however some inputs are still required, particularly during establishment. Perennial warm season grasses also have benefits to biodiversity relative to field crop production by enhancing habitat potential for birds, wild pollinators, small mammals, amphibians and reptiles.

Energy production versus consumption
The energy output to input ratio for biofuels is the total amount of energy contained within the end product (the output), relative to the total amount of energy used in the production and processing of the crop (the input). A higher ratio value is a good indicator of energy sustainability. A range of output:input ratios exist for different bioenergy processes. Fuel produced from switchgrass cellulosic ethanol has the highest output:input ratio at 3.43:1.  Conversely, wheat-based ethanol has a ratio of 1.45:1 and corn ethanol has a ratio of 1.25:1.  The differences between these systems comes from the amount of energy required during production. Switchgrass cellulosic ethanol has less requirements for fossil fuels as part of the plant (lignin) is burned during production to provide the heat and power for the conversion process. Integrating grain based ethanol systems with a biogas plant would also help to improve the conversion energy balance of corn and cereal based ethanol system processing. The energy output:input ratios for grain based ethanol are lower than for bioheat, biogas and biodiesel due largely to the high-intensity of energy used in fermentation and distillation processes.

Understanding the process: from feedstock to end product

The production of ethanol from starch or sugar-based feedstocks is among the earliest ventures into value-added processing for the energy sector. While the basic steps remain the same, the process has been considerably refined in recent years, leading to a more efficient process. (Cellulosic) ethanol can be produced from biomass by the hydrolysis and sugar fermentation processes. Biomass contains a complex mixture of carbohydrate polymers from the plant cell walls known as cellulose, hemi-cellulose and lignin. In order to produce sugars from the biomass, the biomass is pre-treated with acids or enzymes to reduce the size of the feedstock and to open up the plant structure. The cellulose and the hemi cellulose portions are broken down (hydrolysed) by enzymes or dilute acids into sucrose sugar that is then fermented into ethanol. The lignin which is also present in the biomass is normally used as a fuel for the ethanol production plants boilers, and can also contribute some surplus power for sale to the grid.

Conventional ethanol
For conventional ethanol there are two production processes: wet milling and dry milling. Both processes can take place on-farm. The main difference between the two is in the initial treatment of the grain. Wet milling is only used for corn since corn has higher moisture content than barley and wheat, which are generally processed through dry milling.

Wet Miling
In wet milling, the grain is soaked in water and acid for 24 to 48 hours. This steeping facilitates the separation of the grain into its many component parts. After steeping, the corn slurry is processed through a series of grinders to separate the corn germ. Corn oil is either extracted from the germ on-site or sold to crushers who extract it. The remaining fibre, gluten and starch components are further separated. The steeping liquor is concentrated in an evaporator. This concentrated product, heavy steep water, is co-dried with the fibre component and is then sold as corn gluten feed to the livestock industry. Heavy steep water is also sold by itself as a feed ingredient and is used as a component in Ice Ban, an environmentally friendly alternative to salt for removing ice from roads. The gluten component (protein) is filtered and dried to produce the corn gluten meal by-product. This product is highly valued as a feed ingredient in poultry broiler operations. The starch and any remaining water from the mash can then be processed into ethanol. Overall, the fermentation process for ethanol is very similar to the dry mill process described above.

References

Agriculture and Agri-Food Canada. 2006. Ethanol. Market Analysis Division Bi-weekly Bulletin 19 (18).
http://www.agr.gc.ca/mad-dam/index_e.php?s1=pubs&s2=bi&s3=php&page=bulletin_19_18_2006-12-08

Agriculture and Agri-Food Canada. 2007 – Publications: Canada: Grains and Oilseeds Outlook http://www.agr.gc.ca/mad-dam/index_e.php?s1=pubs&s2=go-co&s3=php&page=go-co_2007-06-29&PHPSESSID=b1543ff1c38bb5a67fac59bfbeb4914a Site accessed July 2007.

Zan, C.S., J.W. Fyles, P. Girouard and R.A. Samson. 2001. Carbon sequestration in perennial bioenergy, annual corn and uncultivated systems in southern Quebec. Agriculture Ecosystems and Environment 86[2], 135–144.