Round or Square: A Look at Bale Geometry

Charlie O’Brien
Newsletter Issue: 
November 2014

Truck carrying hay bales

Baling, storing and transportation logistics may seem like run-of-the-mill techniques to today’s agricultural producer. But the steps from the field to the biorefinery are some of the most important in the biomass supply chain, potentially making or breaking a producer’s crop.

When it comes to harvesting, producers need to weigh the economic costs with the logistics of what kind of bales they want to produce: round or square. Both bales’ designs feature unique positive and negative attributes.

Traditionally the 5-by-6 foot round bale has been the most popular bale shape for biomass as it is the cheapest to produce, the easiest to feed livestock with and its round shape helps shed water. Less popular square bales may offer some practical benefits, both for storage and transportation.

“We are trying to reconfigure round bales to make them more logistically efficient,” said Kevin Shinners, professor of agricultural engineering at the University of Wisconsin-Madison and co-project director for CenUSA Bioenergy. “By using a square bale we increase the bale’s density, and the shape is easier to transport.”

Another CenUSA Bioenergy researcher, Stuart Birrell, professor of agricultural and biosystems engineering at Iowa State University, sees bale transportation as an economic issue. When typically transported on flatbed trailers round bales compared to square, are less efficient. Their curved shape creates gaps, wasted space during transit. Birrell suggests that if round bales are continued to be used, the industry should consider adopting specialized trailers from the cotton industry designed specifically to hold large, 8-by-8-foot, round bales.

To increase transportation efficiency in the biomass supply chain, both Birrell and Shinners believe increasing density is a key factor. Round bales are not nearly as dense as square bales, thus causing producers to not use their trailer’s entire weight limit. In the past, Shinners has experimented with large cotton balers that create 5,000--pound bales, a far denser product than the 5-by-6 foot bales that weigh about 1,800 pounds.

“Round bales are also cheaper to produce because its machinery is cheap, but they create a storage and transportation issue. We just have to find out if square bales’ benefits can outweigh its costs,” Birrell said.

In addition to baling logistics, producers need to factor in storage of any biomass material. Both types of perennial grass bales round or square, are able to be stored outside rather than indoors. This additional advantage is due to the crop’s thick natural thatch that sheds water, allowing less amounts of biomass loss.

As biomass in the energy sector progresses, new techniques and practices will be developed to streamline costs and maximize the economic competitiveness of the biofeedstocks. But it’s unlikely that there will be a one size solution to post-harvest logistics.

“It is hard to make a profit with just one kind of crop. You’re looking at all different kinds of biomass crops and it will take all of them to make this a successful industry,” Birrell said.