University of Wisconsin agricultural engineers reported silage storage costs including capital investment and annual costs at various herd sizes. The analysis included hay silage stored in eight different systems (Table 1). Capital costs included structures and equipment used in filling, storing and emptying the hay silage. No transportation, harvesting, or moving feed to the animals were included. Silos and gravel pads had a life expectancy of 20 years while equipment was assumed to have a 10 years of life expectancy. Annual costs include capital costs, labor, plastic coverings, fuel, and dry matter lost during storage. Forage (hay equivalent basis) was valued at $85 a ton. Tractors were assumed to have other uses besides forage storage and allocated on a proportional basis to handle forage storage. Table 1 summarizes total capital and annual costs per ton of dry matter at two different quantities of stored dry matter (four amounts were calculated in original report).
Capital cost per ton of silage dry matter was highest for new steel oxygen-limiting structures compared to other systems. If refilling occurs with steel oxygen-limiting units (1.5 to 2 times annually), costs will be reduced. Used oxygen limiting and cast in place structures were similar. Silo bags, silage piles, and wrapped bales had the lowest investment. No significant economics of scale occurred above 758 tons of dry matter (other storage amounts evaluated were 1536 and 3072 tons). Capital cost per ton can be important on farms where capital is limiting due to expansion and/or existing debt load.
Table 1. Total capital cost and annual cost per ton of dry matter for 384 and 768 tons of stored dry matter (Holmes, 1998).
|Capital Cost||Annual Cost|
|384 tons DM (70 heads)||768 tons DM (140 heads)||384 tons DM (70 heads)||768 tons DM (140 heads)|
|Storage Type||$/ton of dry matter|
|Steel-glass oxygen limiting (new)||427||301||82||60|
|Steel-glass oxygen limiting (used)||268||187||55||41|
|Cast-in-place oxygen limiting||285||186||58||41|
|Above ground bunker||152||103||45||37|
|Packed silage pile||63||41||37||32|