Greenfield’s Ethanol Dry Run

Renewable fuels have come a long way over the past 20 years as rising energy prices have increased the demand for clean alternatives to oil, such as ethanol. GreenField Ethanol has certainly seen it all in its journey to becoming Canada’s leading producer.

GreenField’s Johnstown facility produces more than 200 million litres of ethanol each year and consumes 20 million bushels of locally grown corn.

Begun in 1989, as Commercial Alcohols by Ken Field and a group of investors with a plant in Tiverton, Ont., producing industrial and beverage alcohol, the company opened Canada’s first large-scale fuel ethanol facility in Chatham in 1998 after signing an agreement with a major oil company.

In 2006, Commercial Alcohols was re-named GreenField Ethanol Inc. and over the next two years opened two more ethanol plants in Varennes, Que. (2007) and Johnstown, Ont. (2008).

GreenField produces over 600 million litres of ethanol a year, with 120 million litres being industrial and beverage alcohol. Its Chatham facility has one of only three dry mill continuous ethanol producing plants in North America.

The facility is uniquely capable of alternating between fuel and industrial ethanol production. The Johnstown facility is the largest, producing more than 200 million litres each year and consuming 20 million bushels of locally (within 100 kilometres) grown corn.

Dry mill process
Located along the shores of the St. Lawrence River between Kingston and Montreal, GreenField’s Johnstown facility utilizes a dry mill process designed and built by ICM Inc., a leading ethanol plant engineering firm in North America, which also built GreenField’s Varennes facility – the first ICM project in Canada.

Every truck is weighed going in to and coming out of Johnstown and a sample is taken and tested for moisture content, mould and structure (whole kernel).

In the dry mill process, the entire grain kernel is ground into flour using three Bliss hammermills and the starch in the flour is converted to ethanol during the fermentation process, creating carbon dioxide and dried distillers grain with solubles (DDGS), which are sold for use in making a protein-rich animal feedstock. Johnstown produces about 154,000 tonnes of DDGS per year.

Operating 24 hours, seven days a week, with a staff of 51, Johnstown unloads trucks from 6 a.m. to 6 p.m. Every vehicle is weighed going in and coming out and a sample of each truckload is taken and tested for moisture content, mold and structure (whole kernel).

According to plant manager Darrell Veres, Johnstown has 7,000 kilograms of storage capacity for the corn before the grains are screened to remove debris, then ground into coarse flour in the hammer mill.

The next step is the cooking process, where the starch in the flour is physically and chemically prepared for fermentation.

The milled grain is mixed with process water, the pH is adjusted and an alpha-amylase enzyme is added. The slurry is heated to 83°C or 30 to 45 minutes to reduce viscosity.

The slurry is then pumped using a Sulzer centrifugal pump through a pressurized jet cooker at 105°C and held for five minutes, before being cooled by an atmospheric or vacuum flash condenser.

After cooling, the mixture is held for one to two hours at 85°C to give the alpha-amylase enzyme time to break down the starch into short chain dextrins. Following pH and temperature adjustment, a second enzyme, glucoamylase, is added as the mixture is pumped into one of four fermentation tanks with a capacity of 2.8 million litres each.

Once inside the fermentation tanks, glucoamylase enzyme breaks down the dextrins in the mash to form simple sugars. Yeast is added (30 kilograms for each tank) to convert the sugar to ethanol and carbon dioxide. Urea ammonia is also added for nitrogen, which is food for the yeast. The mash is then allowed to ferment for 50 to 60 hours, resulting in a mixture, known as “beer” that contains about 15% ethanol as well as the solids from the grain and added yeast. The Johnstown facility has a clean-in-place (CIP) system to kill off bacteria and the fermentation tanks are cleaned between fills.

The Johnstown plant has its own quality lab where three technicians test samples of the mash. Process operators do the majority of the analysis to monitor the onoing perfromance of the process.

The fermented mash is pumped into a multi-column distillation system where additional heat is added. The columns utilize the differences in the boiling points of ethanol and water to boil off and separate the ethanol. By the time the ethanol is ready to leave the distillation columns, it contains about 95% ethanol by volume (190 proof). The residue from this process, known as stillage, contains non-fermentable solids and water and is pumped out from the bottom of the columns into one of the four Flottweg centrifuges.

The 190-proof ethanol is then pumped into the molecular sieve system. These specialized vessels contain molecular sieve beads made of ceramic that absorb water molecules from the process stream while ethanol molecules pass through unaffected. When the ethanol leaves the molecular sieves, it is greater than 99% ethanol by volume or 200 proof.

The 200-proof ethanol is pumped to on-site storage tanks where it is denatured or made unfit for human consumption – a legal requirement – and stored until it is ready to be pumped into fuel trucks and hauled away.

The stillage from the distillation system is pumped into centrifuges to separate the majority of the solid matter from the solution. This creates two products: a semi-solid product called wet cake, which is removed and conveyed to a pair of rotary dryers, where it is converted into low-moisture DDGS, and a mostly water process stream, called thin stillage, which is pumped to the evaporation system to be concentrated before being added to
the dryers.