Corn DDGs-A Value Added Functional Material for Wood Composites

Introduction:

In the U.S., the corn dry-grind process contributes to 70% of ethanol production. Nearly 1 kg of DDGS is produced per kg of ethanol. Currently DDGS is utilized locally as feed and protein supplement for ruminant animals. In 2017 DDGS production was 23.2 million tons with selling price of $0.06-0.07 /lb which is below quality wood fiber price of $0.10/0.12 /lb. As predicted by U.S. Grains Council, the availability of DDGS will jump from 10 million metric ton in 2006 to 70 million metric tons by 2020. With increasing DDGS volume, price fluctuations, geopolitical instability, and risk of tariffs it is paramount to identify new avenues to utilize DDGS locally for long term growth and viability of ethanol industry

The main objective of this project is to promote the use of DDGS as a novel functional filler for commercial wood composites. This particular project is focused on utilizing DDGS material for reducing the use of synthetic resin and wax in the particleboards. The main objectives of this project are:

Objectives

1. Identify the optimized use of DDGS to replace paraffin wax and synthetic resin without compromising the physical and mechanical properties of the particleboard.
2. Determine the economic saving associated with the use of DDGS in the particleboards.

An earlier study funded by ND Corn Council proved the feasibility of using DDGS in wood particleboards along with traditional resins such as phenol or melamine formaldehyde. We hypothesized that DDGS can be used to reduce or eliminate the petroleum based resin and paraffin wax in wood composites without affecting physical and mechanical properties of boards. The protein can be functionalized to act as natural adhesive and fat (oil) in DDGS will help to improve the water resistance of particleboards. For this project a graduate research assistant – Joshua Liaw, was recruited from Department of Mechanical Engineering, NDSU. The main project tasks for 2017-19 were as follow. To date we have completed the first two tasks and the third task has just begun.  

Tasks

(1) Identify suitable chemical treatments to functionalize DDGS 

(2) Identify ideal processing conditions for processing DDGS under heat and pressure.  

(3) Design and manufacture DDGS wood fiber composites boards.

(4) Test the physical and mechanical properties of DDGS-wood fiber boards.

All these four tasks will guide and lead us to manufacture DDGS based wood composite boards in the laboratory and evaluate their physical and mechanical properties.

Methods:

Task 1: Identify a suitable chemical method to functionalize DDGS 

In order to utilize the natural adhesive effect of the proteins for bonding and solubilization, protein first needs to be denatured to expose more polar groups. Denaturation involves breaking down of hydrogen bonds, secondary, and tertiary bonds in order to form hydrogen bonds with the wood surface. Some of the widely used methods to denature proteins are to expose it to heat, acid, base, and organic solvents. Based on previous studies and several preliminary experiments we tested several chemical treatments such as alkali, acid and alcohol treatments for functionalizing DDGS. Our initial tests indicated that both the alkali treatment using sodium hydroxide and acid treatment using acetic acid and formic acid are effective treatments. The results on shown in table 1. Our results are in agreement with findings of other authors, who have reported that proteins have stronger adhesive and higher water resistant as compared to unmodified proteins.

Table 1. Physico-mechanical properties of DDGS-Pine wood flour particleboards

Formulation – 50% treated DDGS and 50% pine wood flour. Reported values are average of six samples.

Task 2: Identify ideal processing conditions for processing DDGS under heat and pressure

Since DDGS material consists of fat and protein and they are known to degrade at higher temperature it is essential to identify thermal degradation characteristics of these materials.  During manufacturing of composite boards DDGS will be subjected to hot press temperature ranging from 350°F to 400°F. From the previous study we know that DDGS with particle size 200 micron can handle the particleboard pressing conditions. Once again some preliminary tests were conducted by manufacturing 4 inch by 4 inch test coupons of treated DDGS and pine wood fiber mix at different temperature and pressure conditions. Based on these tests the team identified that best conditions to process the treated DDGS is at 185°C and 12-15 minute of pressure ranging from 1.5 to 4.6 MPa. Currently we are making a new aluminum mold where we can press the particleboards.

Results

The results demosntrate that alkaline conditions (PH-14) or acid conditions (PH-1.8) can be used to uncoil DDGS proteins to bond with hydroxyl groups of cellulosic fibers. The physico-mechanical properties of DDGS:pine (50:50 blend) particleboards are shown in Table 1. The water absorption and internal bond values meet or exceed the ANSI A208.1 particleboard standards and flexural moduli slightly lower for low density boards.

Conclusions

Based on the preliminary results we have concluded that sodium hydroxide, acetic acid and formic acid treatments can be used to functionalize DDGS for use in particleboards. In the coming months (July 2018 to June 2019) the research will focus on manufacturing a large sample size of particleboards with DDGS. A new mold will be used for manufacturing DDGS based wood composite boards. Testing will follow to evaluate the physical and mechanical properties of the boards. Finally the economic analysis will be conducted to estimate the saving wood composite companies can have using DDGS as functional raw material.