Nowadays, there are many ways to generate energy from waste of all kinds. Using waste as a resource to generate energy is a good way to save on raw materials and reduce dependence on fossil fuels, which represent a serious environmental problem due to their carbon dioxide emissions.
An example of this is the Mexican sunflower (tithonia diversifolia), an invasive species in several regions of the world, especially in Africa, Australia and some islands in the Pacific Ocean. Although this plant is a threat to native species in these areas, researchers in Nigeria have found an innovative way to use it: biogas production. By mixing poultry droppings with waste from the Mexican sunflower, they were able to improve the efficiency of the biogas produced.
Generating biogas and improving efficiency
The production of biogas from poultry manure and Mexican sunflowers is a great advantage. On the one hand, waste from poultry farms is used, reducing the pollution they generate. On the other hand, a major environmental problem is tackled: the control of invasive species such as the Mexican sunflower, which displaces local flora.
Studies on biogas production from plant and animal waste have already been carried out in Nigeria and China. The key to these studies is the co-digestion, that is, the use of different types of waste to maximize biogas production. In this case, the studies carried out by Landmark University and Covenant University in Nigeria, published in the journal Energy & Fuels, confirm that the Mexican sunflower has great potential to generate biogas when combined with bird droppings and subjected to prior treatment.
Taking advantage of this combination offers a double benefit because it helps manage waste from poultry farms and slows the spread of a plant considered invasive in many parts of the world. According to experts, Mexican sunflower displaces local species and affects protected natural areas, representing a serious threat to the biodiversity of sensitive regions.
Pre-treatment: Key to improving efficiency
Co-digestion of organic waste is not a new process, but recent studies have shown that the use of a Thermo-alkaline pre-treatment before anaerobic digestion significantly improves biogas yield. This pre-treatment consists of subjecting the waste to high temperatures and specific alkaline conditions, which facilitates the decomposition of complex organic materials and increases the amount of methane produced, the main component of biogas.
The study in Nigeria concluded that biogas yield improved by up to 54,44% thanks to the use of this treatment compared to waste that was not subjected to the same process. In other words, the amount of energy obtained was considerably higher when pre-treatment was used, which is essential if we want to optimize the use of these resources for the generation of energy with a low carbon footprint.
To obtain these results, an energy balance was performed to determine if the energy invested in the process was less than the energy obtained at the end of the process. The data showed a positive energy balance, which means that the process is cost-effective. The energy recovered far exceeded the energy used in the pre-treatment both in the form of thermal and electrical energy.
The importance of poultry waste in biogas production
Los poultry waste play an essential role in biogas production when combined with plants such as the Mexican sunflower. However, it is important to remember that these excrements contain nutrients that, if not properly managed, can be harmful to the environment. These pollutants include: hormones, antibiotics, heavy metals and nutrients which can filter into the soil and water sources, causing pollution problems.
Using this type of waste for biogas generation not only solves the problem of its accumulation, but also offers a cost-effective and sustainable solution to energy production. But one of the most important findings is that while poultry manure alone is not cost-effective, its combination with plant matter, like the Mexican sunflower, significantly increases its profitability.
The impact of invasive plants in other regions
The use of invasive plants for biogas production is not unique to Nigeria. In other countries such as Mexico and Taiwan, ways of using various invasive species to generate biofuels are also being investigated. One example is the water hyacinth or camalote (Eichhornia crassipes), another invasive species that grows rapidly in bodies of water. This type of plants is being used to produce biomethane y ethanol, offering a local and sustainable solution to a global problem.
The use of invasive plants represents a unique opportunity to address the problem of plant pollution and at the same time generate clean energy. These plants can grow without the need for intensive management, making them an affordable and abundant source of biomass.
Other examples of co-digestion: Industrial farms in Europe
In Europe, especially in Spain, several biogas projects have been carried out using waste from industrial farms. In regions such as Castilla-La Mancha, where groundwater contamination by slurry is a growing problem, biogas plants have been used to reduce the environmental impact. However, most of these plants still face challenges, such as the need to import waste from other regions and the high costs of transporting organic waste.
Despite these challenges, biogas has proven to be a viable solution for managing slurry and other waste from intensive livestock farming, which would otherwise be highly polluting.
In municipalities like Ves Raft, where a biogas plant was installed more than a decade ago, has seen a reduction in population due to the installation of these macro farms, showing that although biogas technology is effective, the social and economic impacts must also be considered.
Key factors for efficient biogas production
The success of biogas production depends on several factors:
- Waste management: Ensure a constant flow of raw materials.
- Pre-treatment: Anaerobic digestion is greatly improved when effective pre-treatments are carried out.
- Energy balance: It is crucial to achieve a positive energy balance to ensure the profitability of the project.
- Reduction of environmental impact: Incorporate practices that minimize greenhouse gas emissions and pollutants.
Ultimately, co-digestion of plant and animal waste is a cost-effective, environmentally friendly and efficient solution for biogas production. As further studies such as those conducted in Nigeria and China continue to demonstrate its feasibility, this approach is likely to expand to other regions with similar problems.
In a global context where climate change mitigation is a priority, biogas offers a sustainable alternative to fossil fuels, while solving other critical environmental problems such as the management of invasive species.