First year of transport pipeline injection

The first year of gas injection at BIOMETAGAS LA GALERA has been completed. Gas analyses carried out by an external laboratory throughout the year, especially in the last few months, show that an excellent gas is being produced, with high methane quality and the absence of minority compounds.

In the last months of 2023, between a minimum of 6,500 Nm3/d and a maximum of 10,000 Nm3/d of biomethane has been injected. Productions depends on the availability of raw materials at the biogas plant, with several consecutive days of injections exceeding 9,000 Nm3.

AGF has more than nine years of experience operating biogas plants, three years of experience of injection in UNUE , distribution pipeline, and one year of injection in transport pipeline in LA GALERA.

Milestones achieved in the first years of AGF’s experience.

  • Methane losses in the process considerably lower than 2%, certified at 1.5% although they can reach loss values of less than 1%. Remote operation of the plant is fundamental for the control of process losses.
  • Water consumption between 1-2m3/d. This is a significant improvement when these technologies consume quantities of 1-2m3/h. Even CO2 separation plants of others technologies have higher water consumption, such as membranes if they have inlet gas cleaning.
  • Demonstrated controllability of biomethane quality. The installed instrumentation, the designed control strategy and the implemented control engineering allows to control the CO2 composition in the biomethane stream between 0.3% and 2% fmol. NEDGIA’s distribution network raised the CO2 limit to 2.5% when UNUE had already been injecting for several months, whereas in transport it is necessary to inject a CO2 content of less than 2%.
  • Optimisation of electricity consumption by controlling the composition of the CO2 output.
  • Biogas is processed directly from the biogas plant, without any pre-treatment. The biogas does not pass through an activated carbon filter or any other type of treatment, it goes directly from the biogas plant to the biomethane plant.
  • Water absorption CO2 separation without chemical reaction is a highly adaptable technology with the necessary flexibility for biogas from waste. There is still a lot of room for improvement, with the capabilities of water as a chemical reaction vessel being explored and advanced oxidation systems and other chemical reagents in water being tested to exploit the same process for other treatments of the biogas stream that could lead to large reductions in operating and investment costs.
Compressed biomethane. 

History. Technology Choices and Development.

In 2017 AGF decided to develop its own gas separation technology for the production of biomethane. The motivation for this commitment was based on the possibility of participating in the British market, where it had access to install biomethane plants; and on the impossibility of the Spanish market to assume the costs of European biomethane plants. From a technical point of view, the rigidity of these technologies made them unsuitable for the Spanish market based on waste, not crops; and the possibility of a wide capacity for optimisation of these technologies, which were relatively young, was sensed.

Initially, a membrane technology was developed, an idea that was discarded once the format and business case for this type of biomethane plant was fully understood. Once an agreement was reached with a membrane supplier, this technology was abandoned because it was deficient in terms of control and operation, because of its lack of flexibility and because the business was based on the continuous change of membranes, which meant high operating costs for the projects or costly pre-treatment of the gas, which was unacceptable for the profitability of the plants in those years.

Membrane technology has more publicity because there are more companies offering it, as it is a market that operates on a model similar to that of franchising. Any company that wants to enter biomethane acquires a membrane technology and develops the purchased process, from which it acquires all the technical documentation of the process, which is why they are so linear and similar to each other. At the same time, the membrane manufacturer does not get involved in the development of biomethane plants, so it manages to have a well-developed commercial network. All these plants require periodic membrane changes, or at least they did at the time, and this is what led AGF to discard this technology along with the rigidity of the filtration process, which would present major problems with flow variations.

To reduce membrane degradation, lower maintenance costs and reduce the frequency of membrane changes requires a very clean gas. This requires open cycle water consumption – typical practice in the UK but unfeasible in Spain – and high consumption of activated carbon. All these operating costs were unaffordable in 2017 and 2018 in Spain, when the biomethane sector did not exist and only a few pioneers were breaking new ground.

If anything has been demonstrated over the years, it is that gas is unpredictable, as is the composition of the input material. Variations in the composition of majority elements, but especially of minority elements, make it very difficult to have a stable and clean input gas to the biomethane plant, as in the energy crop-based biogas market. Any biomethane technology that requires a clean input biogas can face many problems in defining correctly the necessary pre- and post-treatments, the management of the residues of these treatments and of the separation media, such as amine-contaminated solutions.

After a thorough study of the technologies, it was decided in 2018 to develop the water absorption process without chemical reaction. The separation medium is water, so the developer is free from any producer of the separation medium. In addition, water is a great chemical reaction medium and the absorption process has a high controllability, as there is no filtration or adsorption. Although amines are more selective than water, water has one great advantage and that is its availability. It can be easily changed and purchased and does not require waste management or the purchase of new solutions each time a change is needed.

After a design phase during 2018 and 2019, the commercialisation of these plants was ready to begin.

The UNUE plant started injecting in 2021.

The second, BIOMETAGÁS LA GALERA, in February 2023.

At the beginning of the injection into the transport pipeline there seemed to be many doubts in the sector about the possibility of injecting a valid gas. The requirements of the transmission pipeline in terms of measurements are higher than those of distribution pipelines. Strict control of the gas introduced into the network has been followed, including real time reading and periodic sampling. The first year of injection into transport has shown that it is possible to do this, but also that it is very complicated and requires the integration of many elements and variables for the success of this injection that are very difficult to foresee.

Biomethane plant. La Galera.

AGF’s proven capabilities.

AGF not only supplies its own processes and technology, but also operates the plants it builds, gets involved with the developers and makes the plants and projects in which it participates its own. Therefore, after several years of injecting gas, it can announce the following points of differentiation:

  • AGF’s remote operation allows for continuous process adaptation, which optimises gas usage. The combination of this capability with the controllability of AGF’s two-stage biogas plants means that no gas is lost at all in most possible situations in biogas plants. The produced biogas must be converted into turnover.
  • The communication between the biogas and biomethane plants allows to work in a constant dome, with a very fine control of productions, flow rates, composition, forecasting, etc. This is especially important in plants that produce 7 days a week but only receive substrates on working days of the week.
  • AGF is the only Spanish company with its own gas separation technology for biomethane production. Furthermore, it is also the only company to offer a compressed biomethane production plant, integrating the high pressure compression module in the plant itself.
  • AGF has experience in virtual pipelines and GV terminals, having developed the La Galera plant to reach up to 250 bar output pressure.
  • AGF has experience in injection into distribution and transmission networks.
  • AGF supplies process plants and subsequently operates them to achieve the maximum possible profitability for developers.
  • AGF is the only Spanish company with the capacity to design, build and operate biogas plants with high efficiency technology and integrate them with biomethane plants.

Making biogas is very difficult, and producing quality biomethane for injection into the gas system also has a considerable level of complexity.

Biogas and biomethane are sectors where process engineering plays a key role.

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