How to Handle Seepage From Farm Silos


Factsheet - ISSN 1198-712X   -   Copyright Queen's Printer for Ontario
Agdex#: 240
Publication Date: 2015/05
Order#: 15-003
Last Reviewed:
History: Replaces OMAFRA Factsheet 04-031, of the same name
Written by: S. Clarke, P.Eng., and D. Hilborn, P.Eng

Table of Contents

  1. Introduction
  2. Seepage is an Environmental Problem
  3. Rate and Volume of Seepage Production
  4. Managing Silo Seepage and Precipitation Runoff
  5. Management of Seepage
  6. Site Locations for Seepage Collection Tanks and vegetated Flow Paths
  7. Sizing of Small Seepage Tanks
  8. Summary

Introduction

Silage seepage presents two concerns for the agricultural industry - water pollution, and corrosion and deterioration caused by the silo silage juices.

When silage is harvested and stored at low moisture contents less than 70% for horizontal silos and 60% for tower silos, there is minimal corrosion and pollution threat. Above this moisture level, significant flow of silage juices (or seepage) from silos may occur (Table 1 and Figure 1). Corrosion happens where the seepage is trapped for a period of time.

The production of seepage can be reduced or eliminated through cropping techniques and harvest timing (see the OMAFRA Factsheet, Harvesting Corn Silage at the Right Moisture).

However, there are conditions where seepage can't be avoided. For example, weather conditions may force a farmer to harvest wet silage or ensile by-products such as sweet corn materials. Both will result in seepage production.

Table 1. Tower silo - maximum moisture content to minimize seepage, whole-plant silages

Silo Size
Max. Moisture Content
3 m x 11 m (12 ft x 40 ft)
72%
4 m x 15 m (14 ft x 50 ft)
70%
5 m x 18 m (16 ft x 60 ft)
68%
6 m x 21 m (20 ft x 70 ft)
66%
7 m x 26 m (24 ft x 85 ft)
63%
9 m x 33 m (30 ft x 110 ft)
60%

Figure 1. Graph with silage moisture content on X axis and effluent produced on y axis. Plotted single line shows effluent produced rapidly increasing as silage moisture content increases.

Figure 1. Horizontal silo - seepage production based on silage moisture content.

Most of the environmental problems associated with silage/haylage seepage on farms come from improper or inadequate collection and retention of the seepage draining from the silos. An adequate collection and storage/treatment system is essential if seepage is anticipated.

Table 2 provides information on the acids in silage seepage that cause silo corrosion. Detailed information on silo corrosion is available in the OMAFRA Factsheet, Deterioration of Concrete Tower Silos.

Table 2. Aggressive constituents of silage seepage

Constituents
Quantity
Lactic acid
4%-6%
Acetic acid
1%-2%
Butyric acid
normally less than 1%
pH
3.5-5.5

Table 3. Constituents of Silage Seepage

Constituents Silage Seepage (typical) Dairy Manure Liquid (typical)
Dry matter 5% (2%-10%) 5%
Total nitrogen 1,500-4,400 mg/L 2,600 mg/L
Phosphorus 300-600 mg/L 1,100 mg/L
Potassium 3,400-5,200 mg/L 2,500 mg/L
pH 4.0 (3.6-5.5) 7.4
Biochemical oxygen demand 12,000-90,000 mg/L 5,000-10,000 mg/L

Source: Cornell University 1994 and OMAFRA

Seepage is an Environmental Problem

In 2013, farmers in Ontario made 5 million tonnes of corn fodder, producing in the process over 20 million L of silage seepage effluent. Silage seepage in an undiluted form has extremely high BOD (biochemical oxygen demand) values, ranging from 12,000-90,000 mg/L (Table 3), which is approximately 60-450 times stronger than domestic sanitary sewage. Even a small discharge of seepage into a watercourse can remove enough oxygen for a fish kill to occur. Reports from Pennsylvania, New York and Ontario have linked silage seepage to fish kills. In addition, cases of silage seepage contaminating wells in Ontario and the U.S. have been reported.

Table 3 shows that seepage contains significant nutrient concentrations (similar to liquid dairy manure). Seepage is an excellent nutrient source for growing crops if properly applied to land. However, similar to other nutrients, seepage can become a pollutant if it enters surface water or groundwater.

Rate and Volume of Seepage Production

The greatest percentage of silage seepage is produced within 5-10 days of storage loading. For normal silage and haylage production, the remaining seepage is usually produced within the following 30 days. The volumes produced are dependent on the vertical pressure in the silo and the initial moisture content of the crop (Figure 1). The addition of acid additives to silage facilitates higher crop moisture, which can result in a higher initial rate of silo seepage.

The ensiling of wetter materials such as sweet corn by-products or corn silage for biogas facilities results in much higher seepage production. This can occur throughout the entire period that the crop is stored.

Seepage flow out of vertical silos is the greatest during the first month of storage. In silos with good internal drainage (i.e., a network of floor drains to carry out leachate), it tapers off after that. Where internal drainage of the silo is poor (or the ensiled material is higher moisture), flow will occur throughout the total storage period as the silo is being emptied. Rainwater on uncovered silage can produce additional effluent.

For horizontal silos, the rain runoff or snow melt from the floor area inside the storage and feed preparation area adds more effluent to the collection system. The highly concentrated effluent base flow will be increased on occasion by rainstorms and snowmelt.

It is important that all the base flow from the silo along with the first flush of precipitation runoff is collected and stored, since this material has higher concentrations of organic matter and nutrients.

Figure 2. Top view of a drawing showing a horizontal silo with floor slopes towards the entry point of the silo. Also shows a weir system that causes low flow (mostly seepage) to move to a seepage collection tank and high flow (mostly precipitation) flowing to a vegetated strip at the bottom.

Figure 2. Horizontal silo front-flow seepage system - diluted liquid to vegetated area.

Figure 3. 45 degree view of drawing of a low flow collection system. This consists of a collection box that conducts the flow to a pipe. The pipe outlets above another pipe placed on a 90 degree angle. If flow is low, all flow from the upper pipe runs into the lower pipe. If the flow rate is high, most of the flow from the upper pipe misses the lower pipe flowing into the vegetated filter.

Figure 3. Low-flow collection system diagram. (Source: AEM)

Figure 4. picture of a low flow system that is described in Figure 8.

Figure 4. Low-flow collection system.

Storage and Treatment of Silage Seepage

Collect the seepage and runoff in a small storage at the silo site and transfer it to an outdoor liquid manure or runoff storage on the farm. Do not contain silage leachate in an under-barn storage (located below animals), because dangerous gases may be produced when the effluent and manure are mixed. Where outdoor liquid manure or runoff storages are not available on the farm, provide a separate storage to contain seepage plus runoff material. During the cropping season, apply seepage on land in the same way as you would apply manure. If seepage is applied to the land, account for the nutrients in the seepage in the Nutrient Management Plan.

Another means of handling and treating seepage involves collecting and storing only the low-flow rates of concentrated leachate from the silo in a storage tank (Figure 2). Allow the diluted high-flow rates of material to flow to a vegetated flow path. Use a low-flow collection system (Figures 3 and 4) to separate the concentrated low-flow seepage.

Reduction of Seepage

Harvest silage/haylage at low moisture:

  • <65% moisture content for tower silos less than 12 m (40 ft) deep
  • <60% moisture content for tower silos over 12 m (40 ft) deep
  • <70% for horizontal silos

Planting shorter-season varieties of corn will result in a drier crop, lowering seepage production. Avoid ensiling wet by-products such as sweet corn residue.

Bunker Silo Sealing/Covering Systems

Using a bunker silo sealing or covering system will reduce silage infiltration by air and water. A sealing system consists of a layer of white or black plastic used as a cover and seal. Old tires are placed edge to edge over the surface of this plastic to help seal the silage.

Figure 5.  Photo of a tarpaulin and sausage bag system for silage protection. This photo shows a large black tarp covering a horizontal storage. Long sand filled bags (shaped like oversize sausages) are shown placed in rows on top of the tarps to keep it down.

Figure 5. Tarpaulin and sausage bag system for silage protection.

Figure 6. Sausage bag placement (drawing). This is a top view of a drawing showing recommended placement of the bags.

Figure 6. Sausage bag placement.

New Silo Sealing System - "No Tires Used"

In this system, traditional plastic sheeting is covered with a second layer. Instead of tires, sausage-bags filled with sand or gravel anchor the cover in place (Figures 5 and 6). The advantages of this system are the added protection, improved sealing, flexibility, and ease of installation and storage of the sandbags.

  • A polyethylene sleeve holds together several of the sausage-bags across the width of a silo. This product reduces the chance of air infiltration between the sausage bags. Figure 6 shows sausage bag placement.
  • Use the sausage bags directly on the silo plastic, to reduce the cost and replace the use of tires. This is a good solution if birds or animals tear the plastic seal.
  • Adding absorbents designed to take up excess moisture will result in very low or no seepage production. Materials include oatmeal, dried sugar beet pulp, dried corncobs, ground corn and hay cubes. To be effective, add enough material to absorb the anticipated seepage. Proper use of these materials is necessary. It may be possible to feed these materials, however, first get proper advice on how to make sure the material is safe as a feed source.
  • On many occasions it may not be possible to wilt the forage adequately or harvest at the desired dry matter content. If the forage is too wet, seepage is likely. Add absorbent materials to "absorb" this seepage. Table 4 lists the water-holding capacity of various materials.

Table 4. Water-holding capacity of various materials

Moisture content
Material
(on an air-dry basis)
Water-holding capacity
(kg/100 kg of material)
(lb/100 lb of material)
10%
Ground corn grain 58
Ground oats 69
Ground wheat 61
Corn cob: Coarse grind (1/2 in.) 143
Corn cob: Medium-to-fine grind 192
Corn cob: Fine grind (1/16 in.) 192
12%
Sugar beet pulp 248
Alfalfa hay 194
Mixed grass hay 195
Oat straw 218

Source: University of Minnesota (1980)

Figure 7. Side view drawing of a vertical silo showing a straw layer placed between the silage and the floor. The drawing shows a tile drain placed inside the silo at the walls that transfers any seepage to an outside storage.

Figure 7. Tower silo seepage storage system.

Managing Silo Seepage and Precipitation Runoff

Recommended practices for managing silo seepage include:

  • Cover the silo - this prevents precipitation from entering and leaching through the silage/haylage.
  • Divert all surface water away from the silo site, as this is considered clean water and does not require collection and storage.
  • For new silos where any seepage is expected, install a seepage collection and storage system as shown in Figures 2, 7 or 8.
  • Inspect the interior silo surface each time the silo is empty for signs of corrosion. Wherever corrosion is severe, recoat the inside of the silo.
  • For horizontal silos, there are several options to manage seepage:
    • Existing horizontal silos: Place a 100-mm (4-in.) tile drain on the floor where the wall meets the silo floor (Option A, Figure 9)
    • New silos: Form holes in the wall to drain silo seepage to an outside drain (Option B, Figure 9.) CAUTION: Protect steel from silage acids with adequate (75 mm (3 in.)) concrete cover.
    • Existing or new horizontal silos with good floor drainage to the front of the silo: Install a catch basin that collects seepage and drains to a long-term storage tank (Figures 3, 4 and 10).
  • Flow may occur throughout the total storage period as the silo is emptied. Diluted flow or flow in periods where seepage is not collected must not directly enter a watercourse or catch basin or run across land with shallow bedrock (Figure 2).

Figure 8. 45 degree view of a horizontal silo seepage system with floor drains that conduct seepage to a catch basin which in-turn pipes it to a collection tank.

Figure 8. Horizontal silo seepage floor-drain collection system.

Notes:
Install cross drains 75 mm x 75 mm (3 in. x 3 in.) on 6-m (20-ft) spacing, filled with 20 mm (7?8 in.) of clear stone. Drain should pick up seepage and first flush of rain runoff.
Drain cross drains to storage tank with header drain 100 mm x 100 mm (4 in. x 4 in.).
Rain runoff from top of storage may be considered as clean water and will not reach the collection system.
Collect, store and spread rain runoff from inside of the storage on cropland.
Treat diluted rain runoff using an approved vegetated filter strip.

Figure 9. Side view of the end of a horizontal silo with in wall holes to an exterior seepage drain which conducts the seepage to a storage.

Figure 9. Outside-drain collection system for existing horizontal silo.

Notes:
(A) 100-mm (4-in.) diameter tile drains placed on silo floor.
(B) Holes in silo walls lead to an exterior covered drain. Collect, store and spread rain runoff from inside storage on cropland. Treat diluted rain runoff using an approved vegetated filter strip.

Figure 10. Top view of a horizontal silo and a feed preparation area. The drawing shows the slopes of the floor. The slopes move any seepage to the front of the bunker then across the front of the bunker to a catch basin which moves the seepage to storage or a clean flow system. The drawing shows slopes towards the front of the bunker to divert water away from the area.

Figure 10. Bunker seepage and clean water run-off system.

Caution: Never mix silage effluent in enclosed tanks, especially tanks within barns, because silage effluent mixed with manure slurry will accelerate the release of hydrogen sulphide gas. Add seepage only to uncovered outdoor storages.

Management of Seepage

Concentrated seepage may have to be mixed with the same amount of water (1:1) for application directly onto crops. Seepage is considered a nutrient, and the amount being applied must be accounted for in the Nutrient Management Plan.

Seepage is also used as a supplementary feed. Due to its high potassium and nitrate levels, only feed seepage after getting expert advice.

Seepage can also be used as an input for a digester system. To avoid operational issues, make sure it is introduced slowly.

Release any dilute material or runoff to a vegetated area. Do not do this if the vegetated area is on shallow bedrock. Make sure adequate distance to surface water or tile drain inlets exists.

Site Locations for Seepage Collection Tanks and Vegetated Flow Paths

As a good management practice, the Environmental Farm Plan recommends:

  • locating seepage collection tanks at a distance of 60 m (200 ft) or greater from surface water (i.e., streams, ditches, ponds or tile inlets)
  • setting separation distances between seepage tanks and wells at 23 m (76 ft) or
  • greater for a drilled well and 46 m (151 ft) or greater for a bored/dug well

Locate storage sites for bagged, wrapped or tubed haylage (baylage) at least 9 m (30 ft) from surface water sources and field drainage tiles to reduce the risk of contamination.

Sizing of Small Seepage Tanks

Install additional storage to deal with wet years when seepage production is higher. Size the storage to include expected seepage volumes and runoff calculated at 0.0015 m3/m2/day (0.005 ft3/ft2/day) for the period of time that the flow is directed to the tank. Often the tank is sized to collect seepage for 1-2 months after the last filling of the silo occurred.

If the material in the seepage storage tank is not used immediately, leave enough freeboard in the tank for direct rainwater entry. Often, a 240-day period is used, requiring 0.6 m (2 ft) of freeboard.

Horizontal Silos
  • If the crop is stored at >80% moisture, size the storage for 10 m3/100 tonnes (320 ft3/100 ton) of crop storage.
  • If the crop is stored at 70%-80% moisture, size the seepage storage for 3.1 m3/100 tonnes (100 ft3/100 tons) of crop stored.
  • If the crop is stored at <70% moisture, use 1.55 m3/100 tonnes (50 ft3/100 tons) of crop stored.

Size a storage to contain seepage and runoff from a horizontal silo measuring 12 m x 30 m x 3.5 m (40 ft x 100 ft x 12 ft) for a 1-month period. Feed preparation apron area is 12 m x 6 m (40 ft x 20 ft). Crop moisture content is 75%. See Tables 5, 6 and 7.

Storage Capacity (T)

T70 = 980 tonnes (1,080 tons) (see Tables 5, 6 and 7)
(storage capacity at 70% moisture)

T75 = 0.3 (T70)/(1-M) (storage capacity at 75% moisture)
= 0.3 (1,080)/(1-0.75)
= 1,180 tonnes (1,296 tons)

Seepage Storage Volume
Seepage = 3.1 m3/100 tonnes x 1,180 tonnes
(100 ft3/100 tons x 1,296 tons)
= 36.5 m3 (1,296 ft3)
Rainfall Storage Volume
= 0.0015 m3/100 tonnes (0.005 ft3/ft2/day)
x 30 days x (area of silo m2 (ft2) + apron area m2 (ft2))
= 20 m3 (720 ft3)

Required Storage Size
= 3.65 m3 + 20 m3 (1,296 ft3+ 720 ft3)
= 56.5 m3 (2,016 ft3)

Seepage and Precipitation Storage Size 614 m3 (2,016 ft3)
Use Table 9 to find the dimensions of the required storage capacity = width x length x height

57 m3 (2,016 ft3) = 4.3 x 4.9 x 2.7 m (14 x 16 x 9 ft)
In addition, a flow path or vegetated area must be available to manage flows during the 11-month period when seepage is not expected. Do not design the flow path over tiles or shallow bedrock.
Figure 11. This shows the screen display for a typical horizontal silo seepage calculation using OMAFRA's NMan computer program.

Figure 11. NMAN source material information for silo seepage.

Seepage Calculations in Software

OMAFRA has a software program called Agrisuite that includes the ability to complete silo seepage calculations. This information is in the MStor worksheet of this software. Figure 11 shows an MStor calculation for information described in Example 1.
Agrisuite is available from the OMAFRA website. Search for Agrisuite.

Tower Silos
  • If the crop is stored at >70% moisture, size the seepage storage for 3.1 m3/100 tonnes (100 ft3/100 tons) of crop stored.
  • If the crop is stored at/or below 70% moisture, use 1.55 m3/100 tonnes (50 ft3/100 tons) of crop stored.
  • The design criteria will give a minimum of 2 days of storage for the seepage material. Provide up to 1 year of storage with very low-moisture crops (i.e., <60% moisture).
    Cover tower silos with roofs to keep out rain.

Example 2:

Size a seepage tank based on the following criteria:

  • tower concrete silo measuring 6 m x 21 m (20 ft x 70 ft)
  • alfalfa silage at 70% moisture
  • see Table 8 for capacity

Storage capacity

= 640 tonnes (703 tons)

Required seepage storage size

= 1.55 m3/100 tonnes x 640 tonnes (50 ft3/100 tons x 703 tons)
= 10 m3 (352 ft3)

Table 5. Capacities for Common Horizontal Silo Sizes (Capacity is in tons for a grass or corn silage density of 45 pounds per cubic ft at 70% moisture)

The following tables list the approximate wet tons capacity for a number of common silo sizes. The tables take into account a 1:2 sloping front face. Widths given are inside to inside and do not include space taken up by posts and planking. When using these tables, calculate the daily feed removal to ensure enough feed is removed to prevent spoilage. For capacity in Tonnes, multiply figures shown by 0.91.

 
Average Silage Density (lbs/cu ft) Silo Height (ft) Silo Width (ft) Removal Rate (tons/day) Silo Capacity (tons)
Silo Length (ft)
4"
/day
6"
/day
12"
/day
100 110 120 130 140 150 160
45 8 20 1.2 1.8 3.6 360 396 432 468 504 540 576
45 8 24 1.4 2.2 4.3 432 475 518 562 605 648 691
45 8 30 1.8 2.7 5.4 540 594 648 702 756 810 864
45 8 40 2.4 3.6 7.2 720 792 864 936 1008 1080 1152
45 8 50 3.0 4.5 9.0 900 990 1080 1170 1260 1350 1440
45 8 60 3.6 5.4 10.8 1080 1188 1296 1404 1512 1620 1728
45 10 20 1.5 2.3 4.5 450 495 540 585 630 675 720
45 10 24 1.8 2.7 5.4 540 594 648 702 756 810 864
45 10 30 2.3 3.4 6.8 675 743 810 878 945 1013 1080
45 10 40 3.0 4.5 9.0 900 990 1080 1170 1260 1350 1440
45 10 50 3.8 5.6 11.3 1125 1238 1350 1463 1575 1688 1800
45 10 60 4.5 6.8 13.5 1350 1485 1620 1755 1890 2025 2160
45 12 20 1.8 2.7 5.4 540 594 648 702 756 810 864
45 12 24 2.2 3.2 6.5 648 713 778 842 907 972 1037
45 12 30 2.7 4.1 8.1 810 891 972 1053 1134 1215 1296
45 12 40 3.6 5.4 10.8 1080 1188 1296 1404 1512 1620 1728
45 12 50 4.5 6.8 13.5 1350 1485 1620 1755 1890 2025 2160
45 12 60 5.4 8.1 16.2 1620 1782 1944 2106 2268 2430 2592
45 14 20 2.1 3.2 6.3 630 693 756 819 882 945 1008
45 14 24 2.5 3.8 7.6 756 832 907 983 1058 1134 1210
45 14 30 3.2 4.7 9.5 945 1040 1134 1229 1323 1418 1512
45 14 40 4.2 6.3 12.6 1260 1386 1512 1638 1764 1890 2016
45 14 50 5.3 7.9 15.8 1575 1733 1890 2048 2205 2363 2520
45 14 60 6.3 9.5 18.9 1890 2079 2268 2457 2646 2835 3024
45 16 20 2.4 3.6 7.2 720 792 864 936 1008 1080 1152
45 16 24 2.9 4.3 8.6 864 950 1037 1123 1210 1296 1382
45 16 30 3.6 5.4 10.8 1080 1188 1296 1404 1512 1620 1728
45 16 40 4.8 7.2 14.4 1440 1584 1728 1872 2016 2160 2304
45 16 50 6.0 9.0 18.0 1800 1980 2160 2340 2520 2700 2880
45 16 60 7.2 10.8 21.6 2160 2376 2592 2808 3024 3240 3456
45 18 20 2.7 4.1 8.1 810 891 972 1053 1134 1215 1296
45 18 24 3.2 4.9 9.7 972 1069 1166 1264 1361 1458 1555
45 18 30 4.1 6.1 12.2 1215 1337 1458 1580 1701 1823 1944
45 18 40 5.4 8.1 16.2 1620 1782 1944 2106 2268 2430 2592
45 18 50 6.8 10.1 20.3 2025 2228 2430 2633 2835 3038 3240
45 18 60 8.1 12.2 24.3 2430 2673 2916 3159 3402 3645 3888

Table 6. Capacities for Common Horizontal Silo Sizes (Silo Length 170-230 ft)
(Capacity is in tons for a grass or corn silage density of 45 pounds per cubic ft at 70% moisture)
Average Silage Density (lbs/cu ft) Silo Height (ft) Silo Width (ft) Removal Rate (tons/day)

Silo Capacity (tons)
Silo Length (ft)

4"
/day
6"
/day
12"
/day
170 180 190 200 210 220 230
45 8 20 1.2 1.8 3.6 612 648 684 720 756 792 828
45 8 24 1.4 2.2 4.3 734 778 821 864 907 950 994
45 8 30 1.8 2.7 5.4 918 972 1026 1080 1134 1188 1242
45 8 40 2.4 3.6 7.2 1224 1296 1368 1440 1512 1584 1656
45 8 50 3.0 4.5 9.0 1530 1620 1710 1800 1890 1980 2070
45 8 60 3.6 5.4 10.8 1836 1944 2052 2160 2268 2376 2484
45 10 20 1.5 2.3 4.5 765 810 855 900 945 990 1035
45 10 24 1.8 2.7 5.4 918 972 1026 1080 1134 1188 1242
45 10 30 2.3 3.4 6.8 1148 1215 1283 1350 1418 1485 1553
45 10 40 3.0 4.5 9.0 1530 1620 1710 1800 1890 1980 2070
45 10 50 3.8 5.6 11.3 1913 2025 2138 2250 2363 2475 2588
45 10 60 4.5 6.8 13.5 2295 2430 2565 2700 2835 2970 3105
45 12 20 1.8 2.7 5.4 918 972 1026 1080 1134 1188 1242
45 12 24 2.2 3.2 6.5 1102 1166 1231 1296 1361 1426 1490
45 12 30 2.7 4.1 8.1 1377 1458 1539 1620 1701 1782 1863
45 12 40 3.6 5.4 10.8 1836 1944 2052 2160 2268 2376 2484
45 12 50 4.5 6.8 13.5 2295 2430 2565 2700 2835 2970 3105
45 12 60 5.4 8.1 16.2 2754 2916 3078 3240 3402 3564 3726
45 14 20 2.1 3.2 6.3 1071 1134 1197 1260 1323 1386 1449
45 14 24 2.5 3.8 7.6 1285 1361 1436 1512 1588 1663 1739
45 14 30 3.2 4.7 9.5 1607 1701 1796 1890 1985 2079 2174
45 14 40 4.2 6.3 12.6 2142 2268 2394 2520 2646 2772 2898
45 14 50 5.3 7.9 15.8 2678 2835 2993 3150 3308 3465 3623
45 14 60 6.3 9.5 18.9 3213 3402 3591 3780 3969 4158 4347
45 16 20 2.4 3.6 7.2 1224 1296 1368 1440 1512 1584 1656
45 16 24 2.9 4.3 8.6 1469 1555 1642 1728 1814 1901 1987
45 16 30 3.6 5.4 10.8 1836 1944 2052 2160 2268 2376 2484
45 16 40 4.8 7.2 14.4 2448 2592 2736 2880 3024 3168 3312
45 16 50 6.0 9.0 18.0 3060 3240 3420 3600 3780 3960 4140
45 16 60 7.2 10.8 21.6 3672 3888 4104 4320 4536 4752 4968
45 18 20 2.7 4.1 8.1 1377 1458 1539 1620 1701 1782 1863
45 18 24 3.2 4.9 9.7 1652 1750 1847 1944 2041 2138 2236
45 18 30 4.1 6.1 12.2 2066 2187 2309 2430 2552 2673 2795
45 18 40 5.4 8.1 16.2 2754 2916 3078 3240 3402 3564 3726
45 18 50 6.8 10.1 20.3 3443 3645 3848 4050 4253 4455 4658
45 18 60 8.1 12.2 24.3 4131 4374 4617 4860 5103 5346 5589

Table 7. Capacities for Common Horizontal Silo Sizes (Silo Length 240-300 ft)
(Capacity is in tons for a grass or corn silage density of 45 pounds per cubic ft at 70% moisture)
Average Silage Density (lbs/cu ft) Silo Height (ft) Silo Width (ft) Removal Rate (tons/day) Silo Capacity (tons)
Silo Length (ft)
4"
/day
6"
/day
12"
/day
240 250 260 270 280 290 300
45 8 20 1.2 1.8 3.6 864 900 936 972 1008 1044 1080
45 8 24 1.4 2.2 4.3 1037 1080 1123 1166 1210 1253 1296
45 8 30 1.8 2.7 5.4 1296 1350 1404 1458 1512 1566 1620
45 8 40 2.4 3.6 7.2 1728 1800 1872 1944 2016 2088 2160
45 8 50 3.0 4.5 9.0 2160 2250 2340 2430 2520 2610 2700
45 8 60 3.6 5.4 10.8 2592 2700 2808 2916 3024 3132 3240
45 10 20 1.5 2.3 4.5 1080 1125 1170 1215 1260 1305 1350
45 10 24 1.8 2.7 5.4 1296 1350 1404 1458 1512 1566 1620
45 10 30 2.3 3.4 6.8 1620 1688 1755 1823 1890 1958 2025
45 10 40 3.0 4.5 9.0 2160 2250 2340 2430 2520 2610 2700
45 10 50 3.8 5.6 11.3 2700 2813 2925 3038 3150 3263 3375
45 10 60 4.5 6.8 13.5 3240 3375 3510 3645 3780 3915 4050
45 12 20 1.8 2.7 5.4 1296 1350 1404 1458 1512 1566 1620
45 12 24 2.2 3.2 6.5 1555 1620 1685 1750 1814 1879 1944
45 12 30 2.7 4.1 8.1 1944 2025 2106 2187 2268 2349 2430
45 12 40 3.6 5.4 10.8 2592 2700 2808 2916 3024 3132 3240
45 12 50 4.5 6.8 13.5 3240 3375 3510 3645 3780 3915 4050
45 12 60 5.4 8.1 16.2 3888 4050 4212 4374 4536 4698 4860
45 14 20 2.1 3.2 6.3 1512 1575 1638 1701 1764 1827 1890
45 14 24 2.5 3.8 7.6 1814 1890 1966 2041 2117 2192 2268
45 14 30 3.2 4.7 9.5 2268 2363 2457 2552 2646 2741 2835
45 14 40 4.2 6.3 12.6 3024 3150 3276 3402 3528 3654 3780
45 14 50 5.3 7.9 15.8 3780 3938 4095 4253 4410 4568 4725
45 14 60 6.3 9.5 18.9 4536 4725 4914 5103 5292 5481 5670
45 16 20 2.4 3.6 7.2 1728 1800 1872 1944 2016 2088 2160
45 16 24 2.9 4.3 8.6 2074 2160 2246 2333 2419 2506 2592
45 16 30 3.6 5.4 10.8 2592 2700 2808 2916 3024 3132 3240
45 16 40 4.8 7.2 14.4 3456 3600 3744 3888 4032 4176 4320
45 16 50 6.0 9.0 18.0 4320 4500 4680 4860 5040 5220 5400
45 16 60 7.2 10.8 21.6 5184 5400 5616 5832 6048 6264 6480
45 18 20 2.7 4.1 8.1 1944 2025 2106 2187 2268 2349 2430
45 18 24 3.2 4.9 9.7 2333 2430 2527 2624 2722 2819 2916
45 18 30 4.1 6.1 12.2 2916 3038 3159 3281 3402 3524 3645
45 18 40 5.4 8.1 16.2 3888 4050 4212 4374 4536 4698 4860
45 18 50 6.8 10.1 20.3 4860 5063 5265 5468 5670 5873 6075
45 18 60 8.1 12.2 24.3 5832 6075 6318 6561 6804 7047 7290

The following table lists the approximate wet tons capacity for a number of common silo sizes.

Table 8a. Estimated Silo Capacities for Forages in Concrete Tower Silos
Silo Diameter X Settled Depth (ft) Alfalfa Silage
(Tons)
40%
m.c.
50%
m.c.
60%
m.c.
70%
m.c.
12 x 30 35 44 57 83
12 x 40 50 62 80 116
12 x 50 63 78 103 150
14 x 40 69 86 113 163
14 x 50 89 111 147 212
14 x 55 99 124 164 237
16 x 50 120 151 199 287
16 x 60 149 186 246 355
16 x 65 162 204 270 389
18 x 50 156 196 260 373
18 x 60 194 243 322 463
18 x 70 232 290 386 554
20 x 60 246 309 409 586
20 x 70 295 371 491 703
20 x 80 345 433 574 821
24 x 60 372 465 615 876
24 x 70 448 562 741 1052
24 x 80 527 660 869 1230
24 x 90 606 759 999 1409
30 x 80 876 1092 1427 1994
30 x 90 1012 1261 1643 2287
30 x 100 1151 1431 1861 2581
30 x 110 1290 1603 2080 2875

Source: OMAFRA Factsheet Tower Silo Capacities, Order No. 88-033.

Table 8b. Estimated Silo Capacities for Forages in Concrete Tower Silos
Silo Diameter X Settled Depth (ft) Corn Silage
(Tons)
55% m.c. 60% m.c. 65% m.c. 70% m.c.
12 x 30 47 54 62 74
12 x 40 66 75 87 102
12 x 50 85 97 111 132
14 x 40 92 106 121 143
14 x 50 121 136 157 185
14 x 55 134 153 175 206
16 x 50 163 184 210 246
16 x 60 200 227 259 303
16 x 65 220 248 284 330
18 x 50 210 238 272 317
18 x 60 261 293 334 388
18 x 70 311 349 397 461
20 x 60 328 369 419 486
20 x 70 393 439 498 576
20 x 80 457 510 579 668
24 x 60 486 543 616 712
24 x 70 582 649 734 844
24 x 80 678 754 850 977
24 x 90 774 860 968 1110
30 x 80 1088 1280 1477 1628
30 x 90 1242 1475 1702 1877
30 x 100 1397 1672 1929 2127
30 x 110 1552 1871 2158 2382

Source: OMAFRA Factsheet Tower Silo Capacities, Order No. 88-033.

Table 9. Seepage and Precipitation Storage Sizes (ft3)

Width Length
(ft)

Height (ft)
1 2 3 4 5 6 7 8 9 10 11 12
5 x 5 25 50 75 100 125 150 175 200 225 250 275 300
6 x 6 36 72 108 144 180 216 252 288 324 360 396 432
7 x 7 49 98 147 196 245 294 343 392 441 490 539 588
8 x 8 64 128 192 256 320 384 448 512 576 640 704 768
9 x 9 81 162 243 324 405 486 567 648 729 810 891 972
10 x 10 100 200 300 400 500 600 700 800 900 1000 1100 1200
11 x 11 121 242 363 484 605 726 847 968 1089 1210 1331 1452
12 x 12 144 288 432 576 720 864 1008 1152 1296 1440 1584 1728
13 x 13 169 338 507 676 845 1014 1183 1352 1521 1690 1859 2028
14 x 14 196 392 588 784 980 1176 1372 1568 1764 1960 2156 2352
15 x 15 225 450 675 900 1125 1350 1575 1800 2025 2250 2475 2700
16 x 16 256 512 768 1024 1280 1536 1792 2048 2304 2560 2816 3072
17 x 17 289 578 867 1156 1445 1734 2023 2312 2601 2890 3179 3468
18 x 18 324 648 972 1296 1620 1944 2268 2592 2916 3240 3564 3888
19 x 19 361 722 1083 1444 1805 2166 2527 2888 3249 3610 3971 4332
20 x 20 400 800 1200 1600 2000 2400 2800 3200 3600 4000 4400 4800
21 x 21 441 882 1323 1764 2205 2646 3087 3528 3969 4410 4851 5292
22 x 22 484 968 1452 1936 2420 2904 3388 3872 4356 4840 5324 5808
23 x 23 529 1058 1587 2116 2645 3174 3703 4232 4761 5290 5819 6348
24 x 24 576 1152 1728 2304 2880 3456 4032 4608 5184 5760 6336 6912
25 x 25 625 1250 1875 2500 3125 3750 4375 5000 5625 6250 6875 7500

Summary

Silo seepage can be a pollutant or safety hazard if managed incorrectly. The methods to properly manage silo seepage include collection, storage and use of the nutrient rich source on the farm and elimination of the liquid seepage.

This Factsheet was revised by Don Hilborn, P.Eng., By-Products Engineer, OMAFRA, Woodstock, and Steve Clarke, P.Eng., Energy & Crop Engineer, OMAFRA, Kemptville.

Do you know about Ontario's Nutrient Management Act?

The provincial Nutrient Management Act (NMA) and the Regulation 267/03 regulate the storage, handling and application of nutrients that could be applied to agricultural cropland. The objective is to protect Ontario's surface and groundwater resources.

Please consult the regulation and protocols for the specific legal details. This Factsheet is not meant to provide legal advice. Consult your lawyer if you have questions about your legal obligations.

For more information on the NMA, call the Agricultural Information Contact Centre at 1-877-424-1300, e-mail or visit our website.

Factsheets are continually being updated, so please ensure that you have the most recent version.


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca