POET Cellulosic Ethanol Plant, United States of America

The US-based biofuel producer POET is planning to build a commercial-scale cellulosic ethanol production plant in Emmetsburg, Iowa. The proposed facility is being developed under the name Project Liberty.

The plant will use corncobs, crop residue, husks and leaves from local sources as feedstock.

POET, previously known as Broin Companies, operates a corn grain to ethanol plant of 55 million gallons per annum capacity in Emmetsburg. The new plant will be built adjacent to this facility and have the capacity to produce 25 million gallons of ethanol per annum. It is expected to substitute about 13.5 million gallons of gasoline every year.

Construction of the plant is expected to begin in August 2011. Start-up is scheduled for mid-2013.

The project will create about 200 jobs during construction and employ about 40 people. It will also generate about $14m additional revenues to the local farmers.

POET operates 27 ethanol production facilities across the US. The company produces about 1.7 billion gallons of ethanol and five million tons of distiller grains per annum.

Funding the commercial-scale cellulosic ethanol production plant

The project is estimated to cost about $261m.

The US Department of Energy granted $80m towards the preparatory works of the project in 2007.

In July 2011, the company received about $105m loan guarantee under a conditional commitment from the department towards realisation of the plant.

Design of the new facility

The Project Liberty aims to demonstrate the viability of ethanol production from lignocellulose feedstock on a commercial scale using biochemical process technology.

The biorefinery will be integrated with the existing dry-grind corn processing plant. It will share existing infrastructure such as utilities and roads. In 2010, the company created an integrated stackyard on a 22-acre site outside its facility for storing the biomass feedstock.

Feedstock used in POET's new plant

The proposed plant will utilise about 700 dry metric tons of lignocellulose a day. The main feedstock will be corncobs. The company is also working with the equipment manufacturers to improve and develop methods to efficiently and sustainably harvest, transport and store the corncobs for commercial production.

About 56,000t of biomass has already been delivered by the local farmers. When fully operational, Project Liberty will annually require 300,000t of biomass.

Project Liberty technology

The plant will use proprietary enzymatic hydrolysis technology for converting the cellulosic feedstock into ethanol. POET has been operating a pilot-scale plant in Scotland, South Dakota since January 2009. The $8m facility produces about 20,000 gallons per annum with corncobs feedstock. It also operates an anaerobic digester.

The life cycle analysis of Project Liberty conducted, by Air Improvement Resource, estimates the plant to be carbon negative. It is expected to reduce the greenhouse gas emissions by 111% when compared to gasoline. Commercial scale implementation of this technology will be demonstrated through Project Liberty. If successful, POET also plans to transfer the enzymatic process to its corn-based ethanol plants.

Process technology

The corncobs and other cellulosic feedstock undergo pretreatment to soften the rigid biomass and make it receptable to further processes.

The feedstock then undergoes hydrolysis and fermentation to break the cellulose into sugars.

Distillation of the ethanol takes place through evaporation and condensation.

The non-fermentable wastes of lignin from the fermentation process are separated. The solid fuel thus obtained undergoes anaerobic digestion to produce biogas.

This gas is used to power both the grain and cellulosic ethanol plants at the site.

The biodegradable liquids from the distillers also undergo anaerobic digestion to produce methane-rich biogas used to generate electricity. The renewable energy thus generated will be sufficient to power both the grain-based ethanol plant and the new plant replacing about 80% of the natural gas.

Contractors involved in the project

The project will be designed and constructed by various POET group companies which include POET Research, POET Design and Construction, and POET Biomass. The commercial enzymes for the process will be supplied by Novozymes. Analytical expertise and training will be provided by the National Renewable Energy Laboratory.

John Deere, Case IH, Vermeer and AGCO will supply the agricultural equipment.