Nopal / cactus

cow and pig

Raw material

Genetically selected, cultivated, nurtured and developed cactus for high biomass production

Manure, waste product

Uses

Livestock food, human food, energy production

Organic fertilizer, energy generator

Retention time

8 – 24 hours

15-20 days

Process temperature

37 °C, controlled temperature

Ambient temperature of 5 – 30 °C, no temperature control

Energy

5 - 15 % of energy consumption is delivered in the process, heat is supplied by hot water from the cooling system of electric generators or boilers

The energy required can be greater than that generated by the system. Heat is delivered by hot water from the cooling system of electric generators,

Facilities

The production of 1 MW of electricity requires 1 reactor of 1300 m3

The production of 1 MW of electricity requires the installation of 15 reactors of 1300 m3

Heating

The electric generators generate more than 200 % of the heat needed for the process. Only a fraction is used for reactor heating

The heat is delivered by hot water from the cooling system of electric generators, but it is insufficient to maintain a stable mesophyte temperature. It will require 15 times more hot water to heat 15 reactors and produce the same energy

Materials

It uses carbon steel, cactus does not produce hydrogen sulfide, equipment that uses natural gas is suitable.

Stainless steel or Teflon must be used in the entire process line in contact with biogas, biodigesters, purifying blowers, electric generator

Waste

Approximately 1 % of cactus is not processed, it contains lignin or fibers digestible by bacteria, 99 % is water or biomass that is transformed into water with nitrogen, nutrients and usable biogas. This effluent is odorless and is used in plantations, it is recycled

The material digested by the bacteria depends on the feed of the animals and their composition. It usually has a strong rotten egg smell corresponding to hydrogen sulfide. 80% of the materials are transformed into non-processable sludge. This requires waste disposal.

Production capacity

The process is elastic and can be regulated from 10% to 100% of the installed capacity. Production is adjusted by feeding reactors, if more energy is required, more cactus is cut and fed to reactors, there is no accumulation of material, the cactus remains in plantations until it is necessary to cut it.

The process is adjusted to the number of animals and excreta generated daily, the accumulation of excreta generates environmental problems, therefore everything produced must be processed. It is not possible to increase or decrease the number of animals daily. It is a more rigid process.

Scalability

If there are available surfaces, cactus can be planted and energy can be produced

Scalability is limited to the number of animals and their excreta.

System stability

Operating with cactus feeding, the systems are stable for years. The raw material is stable. It uses continuous reactors.

They are sensitive to the antibiotics used for the main activity of animal husbandry, which can cause the total detention of bacteria inside reactors. Likewise, temperature variations affect energy production.

Maintenance

The equipment is similar to that used in natural gas, therefore its maintenance is very low and they are long-lasting. The reactors operate for years without stopping. The designs use locally available materials and equipment.

It requires greater maintenance of the equipment in contact with the H2S of biogas, spare parts are more expensive when using stainless steel. Imported equipment with resistance to corrosive materials.

Digesters

They are specific for cactus considering its rheological characteristics and biogas composition, bacterial catalysts and construction materials

They are usually designed for various excreta from both cows and pigs, they are the most common, there are multiple designs according to the characteristics of the areas and especially process temperatures.