Biogas for Pig, Poultry and Feedlot Operations
Turn manure from your pig, poultry or feedlot operation into energy and biofertilizer. Technical guide to covered lagoons and CSTR reactors for manure management.
Manure from a pig, poultry or feedlot operation is both an environmental liability and an energy resource. A biodigester converts it into biogas (55–65% methane) for thermal or electrical energy, and into digestate, a stabilized biofertilizer. The two most common setups in the sector are the covered anaerobic lagoon (for dilute slurries, low cost) and the CSTR reactor (for more concentrated substrates and higher yield per m³). The choice depends on the species, how manure is handled and the energy goal.
The livestock sector challenge
Each species produces a waste with different characteristics, and that drives the technology:
- Pigs: liquid slurry with plenty of wash water. High but dilute organic load; ideal for a covered lagoon or CSTR depending on solids concentration.
- Poultry: broiler litter or layer manure, drier and rich in nitrogen. High biogas potential, but needs ammonia control and often co-digestion to balance the C/N ratio.
- Feedlots (beef cattle): solid manure with lignocellulosic material; usually combined with other substrates and requires good mixing.
Untreated, these wastes generate odors, attract vectors, emit methane to the atmosphere and strain the environmental license. A biodigester captures that methane and turns it into useful energy.
The Tech Tank solution: turnkey biodigestion
Tech Tank designs and integrates turnkey biogas plants —engineering, reactor, gas holder, flaring/valorization and installation— tailored to each farm's profile. The two main routes:
Covered anaerobic lagoon
A lined lagoon sealed with a geomembrane and topped with a flexible cover membrane; biogas accumulates under the cover and is drawn off. It is the lowest-CAPEX option for dilute pig slurry, with long retention times (20–40 days or more) and low operating demand. The cover also controls odors and emissions.
CSTR reactor
The continuously stirred tank reactor (CSTR) keeps the substrate fully mixed at a controlled temperature (mesophilic ~35–40 °C). It offers higher organic loading rate and biogas yield per m³, ideal for poultry manure, co-digestion or where land is limited. It is typically built in a bolted steel tank.
Biogas valorization
Biogas feeds an engine-generator (CHP) for power and heat, fires boilers, or is upgraded to biomethane. Digestate is applied as biofertilizer, closing the nutrient loop on the farm itself.
Benefits with data
Biogas potential depends on the substrate's volatile solids (VS). Indicative specific-yield ranges:
| Substrate | Biogas (m³ per kg VS) | Typical technology |
|---|---|---|
| Pig slurry | 0.25–0.50 | Covered lagoon / CSTR |
| Poultry manure / litter | 0.30–0.55 | CSTR (co-digestion) |
| Cattle manure (feedlot) | 0.20–0.40 | CSTR |
At 55–65% methane, each m³ of biogas is worth roughly 5.5–6.5 kWh of primary energy. Converted to electricity in a CHP unit (electrical efficiency ~38–42%), a m³ of biogas yields on the order of 2.0–2.4 kWh of electricity. Exact figures depend on substrate, temperature and design; they should be estimated from each farm's real characterization.
Co-digestion: more energy per reactor
Mixing manure with other on-farm residues —crop leftovers, glycerin, food-processing waste, energy crops— is called co-digestion, and it can lift biogas output well above what manure alone delivers. It also balances the carbon-to-nitrogen (C/N) ratio, which is especially useful with nitrogen-rich poultry manure that would otherwise risk ammonia inhibition. A CSTR handles co-digestion better than a lagoon because it keeps everything fully mixed and at controlled temperature. The trade-off is a slightly more demanding operation, so the substrate recipe is defined during design from what each operation actually has available.
Environmental and economic benefits
- On-site energy: cuts the operation's electricity and fuel bills.
- Odor control: the cover and anaerobic digestion sharply reduce bad odors.
- Biofertilizer: digestate replaces mineral fertilizer and improves nutrient logistics.
- Compliance: methane capture and better manure management before MADES.
Regulation
In Paraguay, biogas projects and livestock effluent management fall under Law 294/93 (Environmental Impact Assessment) and Law 3239/07 (Water Resources), licensed by MADES. We recommend verifying current regulations and license requirements with MADES before starting the project.
From waste to return
A well-sized biodigester is not just treatment: it is an investment with a return. To understand the technology in depth, read what an industrial biodigester is and, to assess profitability, the guide to biodigester payback in agribusiness. Full detail on equipment and installation is in our biogas and biodigesters solution.
Want to know how much energy your farm could produce? Get in touch with your animal numbers and manure handling, and we will prepare a yield estimate and a turnkey proposal.
Frequently Asked Questions
Covered lagoon or CSTR for a pig farm?
It depends on slurry concentration and the goal. The covered lagoon costs less and suits dilute slurry with plenty of wash water; the CSTR produces more biogas per m³ and is better for concentrated substrates, poultry manure, co-digestion or limited land.
How much biogas does manure produce?
As a guide, pig slurry yields 0.25–0.50 m³ of biogas per kg of volatile solids, poultry manure 0.30–0.55 and cattle manure 0.20–0.40. The real value depends on diet, manure handling, temperature and retention time.
What do I do with the digestate?
Digestate is a stabilized biofertilizer, rich in available nutrients. It is applied to the farm's own soil in place of mineral fertilizer, closing the nutrient loop. Its handling must follow good practice and environmental regulations.
Does biogas reduce farm odors?
Yes. Covering the lagoon or digesting the slurry in a closed reactor captures the gases and sharply reduces bad odors compared with open storage, while also preventing methane release to the atmosphere.
Can I generate electricity from the biogas?
Yes. With an engine-generator (CHP) biogas produces both electricity and usable heat. As an order of magnitude, each m³ of biogas yields 2.0–2.4 kWh of electricity, depending on methane content and equipment efficiency.