Watertight Silage Silos with Acid-Resistant EPDM Membrane
EPDM membrane for bunker silos, clamp silos and silage pits resists organic fermentation acids (pH 3-4.5) for 50+ years — protecting concrete, containing leachate and ensuring compliance with Portugal's REAP regulation and the EU Nitrate Directive.
The Silage Silo Challenge
Silage storage structures are exposed to organic fermentation acids (lactic, acetic, propionic) at pH 3-4.5 that attack unprotected concrete. Without adequate protection, concrete deteriorates within 15-20 years, creating forage contamination, leachate seepage to soil, and active environmental liability. Silage leachate has a BOD5 of 10,000-70,000 mg/L — more than 200 times the load of raw municipal sewage.
- Lactic and acetic acid (pH 3-4.5) react with cement calcium hydroxide — progressive concrete surface dissolution, aggregate exposure and structural cracking in 15-20 years
- Silage leachate with BOD5 of 10,000-70,000 mg/L penetrates cracked soil and contaminates aquifers and watercourses — severe environmental and legal consequences (DL 147/2008)
- Conventional epoxy coatings crack at construction joints through thermal movements of 12-18 mm in 30 m walls — concrete continues to suffer acid attack beneath the cracked coating
- PVC liners with 20-40% plasticiser by weight lose flexibility at fermentation temperatures (40-70°C) — plasticisers migrate into silage, compromising forage quality
- REAP non-compliance (Decree-Law 81/2013) can result in fines up to €100,000 for companies — EPDM installation represents a fraction of this regulatory risk
The EPDM Solution for Silage Silos
EPDM creates an impermeable chemical barrier between silage and concrete. The saturated polymer chain without C=C double bonds has no reactive sites for organic acids — intrinsic resistance confirmed by ASTM D471 tests at pH 2.5 and 70°C. 1.5 mm EPDM on walls and 2.0 mm on floor (tractor traffic) — impermeable continuity at the critical wall/floor junction with pre-formed corner cove strips.
- Intrinsic resistance to lactic, acetic and propionic acid — ASTM D471 tests at 70°C/pH 2.5 show zero measurable degradation: no change in Shore A hardness, tensile strength or elongation
- 400% elongation — accommodates seasonal thermal movements of 12-18 mm in 30 m walls and foundation settlement without coating cracking
- Integrated leachate collection system — EPDM drain with compression flange at lowest floor point, connected to farm collection system
- Complete technical documentation for PGEP and DRAP/APA licensing — installation report, EN 13956 datasheet and warranty certificate
EPDM Benefits
Intrinsic Fermentation Acid Resistance
EPDM resists lactic, acetic, propionic and butyric acids at fermentation concentrations for decades without measurable degradation. ASTM D471 tests at 10% lactic acid / pH 2.5 / 70°C (equivalent to 25+ years real service by Arrhenius projection): zero change in hardness, tensile strength or elongation. Resistance is intrinsic to molecular structure — not dependent on coatings or surface treatments.
Total Leachate Containment — REAP Compliance
Complete silo waterproofing prevents leachate (BOD5 10,000-70,000 mg/L) infiltration into soil and aquifers. Full compliance with Decree-Law 81/2013 (REAP) and EU Nitrate Directive (91/676/EEC). The Membriko technical dossier — EN 13956 datasheet, photographic record, installation report and 15-year warranty — provides exactly the documentation DRAP inspectors require for PGEP approval.
Forage Protection — Silage Inertness
EPDM formulated without plasticisers (no phthalates, no adipates) and without heavy metal stabilisers. Migration tests confirm no detectable compounds in silage at concentrations significant for animal nutrition. Declaration of conformity with Regulation (EC) 1935/2004 and Feed Hygiene Regulation 183/2005 available in the installation dossier.
Fermentation Temperature Resistance
Active fermentation in the first 15-45 days after filling generates 40-70°C internally (peaks of 70°C in high-DM silage poorly sealed). EPDM with service temperature of -45°C to +130°C covers these extremes with 60°C safety margin. Hot lactic acid (70°C) is significantly more aggressive than at ambient temperature — precisely the conditions under which EPDM demonstrated zero degradation in ASTM D471 testing.
Wall/Floor Junction with Full Continuity
The wall-to-floor junction is the highest-risk point in any silo — maximum tensile stress from silage pressure, thermal movements and settlements. Membriko installs a pre-formed EPDM cove strip (minimum 20 mm radius) at the internal corner before main membranes — eliminating the stress concentration point that destroys rigid coatings. Continuous impermeable barrier without discontinuity points.
Structural Investment Protection
A concrete bunker silo represents a €20,000-€60,000 investment. Without EPDM protection, acid attack compromises structural integrity within 15-20 years requiring reconstruction at similar cost. EPDM installation cost (€4,500-€35,000 depending on size) protects the structural investment for a fraction of the risk, with documented 50+ year service life.
Technical Specifications
Thickness (walls)
1.5 mm (EN 1849-2)
Thickness (floor with tractor traffic)
2.0 mm (EN 1849-2)
Lactic acid resistance (pH 3)
No degradation after 1,000 h immersion (ASTM D471)
Acetic acid resistance (pH 3.5)
No degradation after 1,000 h immersion (ASTM D471)
Elongation at break
≥ 400% (EN 12311-2) — accommodates thermal and substrate movements
Service temperature
-45°C to +130°C — covers full fermentation range
Silage inertness
Confirmed — no detectable migration (per EN 13956)
Product standard / CE marking
EN 13956
Installation Process
- 1
Free Technical Visit and Survey
Free technical site visit to the silo. Exact dimension survey: length, width, wall height, front face configuration. Concrete condition assessment: previous acid carbonation, cracks, construction joints, structural deterioration. Identification of existing leachate drain position or new system design. Traffic pattern assessment for floor thickness specification (1.5 mm without tractor traffic; 2.0 mm with traffic).
- 2
Project Design and Cut Plan
Membrane cut plan preparation (EPDM panel layout minimising seams, complete wall and floor coverage). Detailed materials specification: 1.5 mm EPDM walls, 2.0 mm EPDM floor, cove strips, anchoring and drainage accessories. List of concrete preparation works required before installation (repairs, edge chamfering). Technical documentation for PGEP.
- 3
Concrete Surface Preparation
Grinding or milling of irregular concrete surfaces. Crack filling >5 mm with flexible mortar (elastic modulus compatible with EPDM). All sharp internal corners rounded to minimum 20 mm radius — sharp corners create membrane stress concentration in service. High-pressure water jetting to remove calcium carbonate deposits from previous silage cycles. On surfaces with severe acid carbonation, neutralising wash before adhesive application.
- 4
Wall Membrane Installation
1.5 mm EPDM wall panels installed from top of wall downwards. Galvanised steel top anchor bar mechanically fixed to concrete with expansion anchors, sealed with double-thickness EPDM flashing. Panels bonded to wall with contact adhesive formulated for EPDM in acid environments. Vertical seams: 150 mm overlap with vulcanised QuickSeam tape and activator primer (peel strength ≥ 0.6 N/mm). At wall/floor junction, pre-formed EPDM cove strip for continuous, unstressed transition.
- 5
Floor Membrane Installation
2.0 mm EPDM floor panels installed with minimum 1% slope towards leachate collection point. Floor membrane seamed to wall membrane through the cove strip installed in the previous step, creating continuous barrier. At leachate drain point: EPDM drainage fitting with compression flange — testable watertight connection between membrane and drainage pipe, sealed across a 200 mm radius from drain centre.
- 6
Leachate System, Testing and Documentation
Leachate drainage pipe connected to farm collection system (channel, sump or tank). Slope and watertightness verification of entire installation. Documented hydraulic test for compliance process. Issue of photographic installation report and 15-year warranty certificate — documents that form part of the environmental compliance dossier for PGEP and DRAP/APA inspections.
Installation Techniques
Fully Bonded EPDM in Concrete Bunker Silo (Standard System)
1.5 mm EPDM on walls + 2.0 mm EPDM on floor, fully bonded to concrete with acid-environment adhesive. Pre-formed cove strip at wall/floor junction. Standard system for bunker silos with smooth, regular concrete.
Vantagens
- Complete concrete protection from fermentation acids — concrete service life extended indefinitely
- Smooth surface for easy cleaning and disinfection between fills — reduces secondary Clostridium fermentation risk
- Pre-formed cove strip eliminates highest-risk failure point — wall/floor junction with full continuity
- Complete documentation for PGEP and REAP compliance included in installation
Desvantagens
- Requires regular, clean concrete — surfaces with severe deterioration need prior epoxy mortar repair
- Full bonding requires adequate temperature conditions (>10°C) for correct adhesive cure
EPDM in Clamp Silo (Horizontal Silo)
For clamp silos (open horizontal silos with temporary side walls), 1.5-2.0 mm EPDM on the concrete base slab with perimeter extension to upstand behind side walls. Perimeter leachate collection channel integrated in the installation detail.
Vantagens
- Total leachate containment even without permanent walls — perimeter upstand prevents edge escape
- Fast installation in low capital cost silos with existing concrete slab
- Good sealing even on slabs with irregularities — 400% elongation accommodates differential settlements
Desvantagens
- Vertical parts of temporary walls or earth banks require specific membrane anchoring
- Silage cover separate (plastic film) — EPDM does not function as the top cover of a clamp silo
EPDM in Below-Ground Silage Pit
For excavated silage pits in favourable topography, 200 g/m² protective geotextile between excavated sub-base and 1.5 mm EPDM. In areas with high water table, drainage layer beneath geotextile to relieve membrane uplift pressure.
Vantagens
- Natural thermal stability from surrounding soil — more moderate internal temperature range than surface silos
- Lower structure construction cost than concrete-walled bunker silos
- Protective geotextile prevents puncture by stones and roots in excavated surface
Desvantagens
- Work on inclined slopes requires specific membrane anchoring to prevent slippage
- In areas with high water table, sub-membrane drainage required to prevent hydrostatic uplift
Comparison with Other Membranes
| Característica | EPDM | Bare concrete | Epoxy coating |
|---|---|---|---|
| Lactic acid and fermentation resistance | Excellent — pH 3-12; no degradation at 70°C/1,000 h (ASTM D471); 50+ years | Poor — progressive cement dissolution; visible deterioration in 5-8 years; structural failure in 15-20 years | Good when intact — but zero elongation; cracks at thermal construction joints; reapplication at 8-15 years |
| Thermal movement accommodation | 400% elongation — accommodates ±12-18 mm in 30 m walls without cracking | Zero elongation — cracks at construction joints through annual thermal movements | 12-15% elongation — seam cracking risk under substrate movement |
| Silage inertness (animal feed safety) | Confirmed — no plasticisers, no detectable migration; per Regulation 183/2005 | Risk — 20-40% by weight phthalate plasticisers migrate into silage at 40-70°C fermentation temperatures | Variable — lime and calcium hydroxide migration into silage; raises silage pH |
| Leachate containment — REAP/DRAP compliance | Total — zero permeability; complete documentation for PGEP included in installation | Poor — porous and cracked; not accepted by DRAP as documented watertight containment system | Conditional — acid and thermal movement cracking; long-term compliance not sustained |
| 30-year life-cycle cost | Index 100 — single installation without re-intervention | Index 180 — concrete rebuild/repair cycles at 15-20 years | Index 160 — 3 reapplications in 30 years at €15-25/m² each |
| Active fermentation temperature (40-70°C) | No degradation — service temperature to +130°C; 60°C margin above fermentation peak | Accelerated degradation — fermentation temperature accelerates plasticiser migration | Good resistance at 40-70°C, but becomes brittle below -15°C (northern upland winter nights) |
Performance in the Portuguese Climate
North — Minho, Braga and Entre Douro e Vouga (Intensive Dairy)
Northern Portugal has the highest density of dairy farms in the country, with maize and grass silage as the basis of winter feeding. Bunker silos of 30-60 m length and 4 m wall height are common in this region. Annual rainfall of 1,200-2,000 mm and winter temperatures of -2°C to +5°C create conditions of prolonged active fermentation and severe thermal movements in concrete walls. EPDM with 400% elongation and -45°C to +130°C service temperature is the only membrane that covers this entire range.
Trás-os-Montes and Beira Interior (Extensive Beef Cattle)
Extensive beef cattle farms in the northern interior store seasonal silage for winter supplementation and drought periods. Smaller silos but exposed to extreme winter temperatures (-5°C to -15°C on high-altitude nights). EPDM with -45°C minimum service temperature does not become brittle in these conditions — HDPE can become brittle below -15°C, a relevant risk on Trás-os-Montes highlands.
Centro — Coimbra, Leiria and Santarém (Mixed Production)
The central region combines intensive dairy farming with beef cattle and small ruminants. Membriko, based in Pombal in the Leiria district, has extensive installation experience in silos across this region. Moderate summer temperatures (35-38°C) but active fermentation at 60-70°C in the first months after filling. Centro-Oeste soils with expansive clays create foundation settlements that EPDM with 400% elongation accommodates without cracking.
Alentejo (Intensive Pig Farming and Extensive Cattle)
Intensive Alentejo pig farms with large silage volumes as feed supplement (maize, grass, olive marc). Extreme summers with air temperatures of 42-45°C accelerate active fermentation and increase leachate concentrate aggressiveness. Alentejo pig farms face stringent environmental regulation — the Membriko technical dossier is particularly valued in DRAP Alentejo inspections.
Nitrate Vulnerable Zones (NVZ) — Tejo, Douro and Ria de Aveiro
On farms in NVZ-designated areas (under EU Nitrate Directive 91/676/EEC), silage leachate containment is not an option — it is a legal obligation with compliance deadlines. EPDM with zero permeability and complete technical documentation for PGEP is the solution DRAP accepts as documented proof of watertightness. Membriko has extensive experience in NVZ compliance projects across Portugal.
Frequently Asked Questions
Yes. Membriko-installed EPDM is formulated without plasticisers (no phthalates, adipates or other plasticisers), without heavy metal stabilisers (no lead, cadmium or tin) and without biocides. Suppliers that Membriko works with provide declarations of conformity with Regulation (EC) 1935/2004 and Feed Hygiene Regulation 183/2005. For certified organic farms, Membriko provides the material composition datasheet for submission to the certifier.
Yes. Decree-Law 81/2013 (REAP — Livestock Activity Regulation) and Decree-Law 235/97 (implementing the Nitrate Directive) require that livestock installations with Effluent Management Plans (PGEP) have watertight storage systems, including for silage leachate. In Nitrate Vulnerable Zones, requirements are even stricter. Membriko EPDM + collection system ensures documented compliance.
Both. Laboratory data: ASTM D471 testing in 10% lactic acid solution at pH 2.5 and 70°C for 168 hours — conditions more severe than any real silo (pH 3-4.5, maximum temperature 70°C). Result: zero change in Shore A hardness, tensile strength and elongation. By Arrhenius projection, these conditions represent 25+ years of real service. Field data come from EPDM membranes in silage silos in service in Europe for 30+ years without intervention. Membriko makes both types of data available in the installation dossier.
With a pre-formed EPDM cove strip. Membriko installs an EPDM corner profile with minimum 20 mm radius at all internal corners before main membranes. This cove eliminates the stress concentration point that would occur at a sharp corner in service — where silage pressure, thermal movements and any settlements create maximum tensile stress. The cove is bonded with the same adhesive as the membranes and seamed with QuickSeam tape, creating a continuous transition without discontinuity points between wall and floor.
Yes, with the correct specification. Membriko specifies 2.0 mm EPDM on floors with regular tractor and loading shovel traffic during filling and emptying. This thickness, combined with EPDM tear resistance (≥ 20 N/mm per EN 12310-2), withstands agricultural machinery traffic. In zones with very intensive passage or high-pressure rubber tyres, Membriko can specify an additional protective geotextile layer (300-500 g/m²) above the membrane.
Initial epoxy coating cost may be 20-30% lower than EPDM. But the 30-year life-cycle cost tells the complete story: epoxy requires reapplication at 8-15 years (€15-25/m² each) and does not solve the construction joint cracking problem — concrete continues to suffer acid attack beneath the cracked coating. Membriko estimates the 30-year life-cycle cost of epoxy at 160% of EPDM cost (base index EPDM = 100). A single EPDM installation with 15-year warranty is economically superior to the cycle of epoxy reapplications.
Yes. The Membriko technical dossier delivered with each installation includes all documents required for PGEP: EPDM membrane technical datasheet (EN 13956, CE performance declaration), installation description (construction system, thicknesses, overlaps), georeferenced photographic record (before, during and after installation), hydraulic watertightness test report and 15-year warranty certificate. This package is exactly what DRAP and APA inspectors request to validate effluent storage structure compliance.
A bunker silo 20 m long × 5 m wide × 3 m wall height has approximately 500-600 m² of membrane area (walls + floor). With concrete prepared, the Membriko team completes installation in 3-4 days. Including concrete preparation works (crack repair, edge chamfering, cleaning), total is 5-7 days. The silo can be filled with silage immediately after installation completion — no curing time required.
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