Stover Quality

Harvest Window

Corn stover harvest in Iowa is an annual occurrence as it can only be completed after grain harvest.  The window of time during which all shredding, windrowing, baling, and moving bales to storage sites must be completed is relatively small.  This window is estimated to be an average of 4 weeks (28 days) after grain harvest depending upon field availability and weather changes.  More details on the corn stover harvest time window are available in Publication PM 3051B - Corn Stover Harvest Window.  

Ash Content

Good baling practices must be used when producing corn stover bales irrespective of the harvest window as the bales must last in storage until the next harvest occurs.  Appropriate clearance above the ground surface must be maintained when using harvesting equipment to minimize the amount of soil contamination in the corn stover.  Ash content of the baled stover due to soil and rocks can render the quality as unacceptable for industrial purposes.  Industry specifications must be adhered to when considering participation in the corn stover supply chain. Industries are accepting bales with ash content from 8 to 15 percent depending upon use, with severe penalties for higher ash content.  Commercial corn stover harvest teams of trained personnel are currently forming to provide custom baling operations.  The use of such custom operations employing trained staff may help with controlling the ash content of the baled stover.  A corn stover ash content analysis for different baling methods including structural and non-structural ash is available in Publication PM 3051L - Corn Stover Ash.

Storage and Moisture Content

Moisture content of the stover at the time of baling influences storage losses over time.  In addition, the method of storage, i.e., outdoors, outdoors and under tarp, under roof, and in airtight wrapping, can yield different dry matter loss. Storage losses can cause disintegration of bales.  No matter which method is used to store bales, it must be managed properly to minimize dry matter loss.  A comparison of different methods of corn stover bale storage and how the dry matter loss is affected by stover moisture is presented in Publication PM 3051E - Corn Stover Storage Losses.  Industrial plants in Iowa will typically accept bales with less than 22 percent moisture with minimal or no penalty, but will assess penalties for higher moisture content including rejection of the entire load.  Different microwave moisture meters available in the market can be used to determine moisture content.  Publication PM 3051M - Methods for Rapid Moisture Analysis presents a comparison between capacitance based moisture meters (typically used for hay bale moisture determination) and microwave moisture meters.

Fire Hazard

The presence of large bales of dry biomass in one location presents a fire hazard and can potentially result in the loss of all bales in one location.  When making decisions on how to create corn stover bale stacks, attention must be paid to stack size, spacing between stacks, and distance from other buildings and combustible materials.  Publication PM 3051F - Fire Risk in Corn Stover Storage summarizes best practices and makes recommendations for locating corn stover biomass storage facilities.