Production of bio energy from poultry manure with additional value creation through recycling of fermentation residue

Advantages of the GMS alpha process

1. Resources

Exclusive processing of poultry manure has a clear procurement cost advantage as compared with maize, for example, and therefore has a significantly better economic starting situation!

In addition, with poultry manure there is no advance investment for sourcing a silo annually, and even procuring poultry mist is generally less problematic than in the case of Nawaro silage. Poultry manure accumulates in large quantities all year round as a by-product of commercial poultry farming, independent of the impact of the weather and harvest yields. Delivery can take place directly from production sites to the plant with buffer provisioning of 6 – 10 days. Closed temporary storage avoids the emission of odours and the spread of pathogenic germs into the environment.

With the GMS alpha processes, separate, processed waste water from the plant is used as process liquid; liquid manure does not need to be used, meaning that its delivery, storing and discharging costs are avoided all together. Overloading the ground with nitrogen together with nitrification of groundwater and eutrophication of open bodies of water is avoided.

2. Mechanical disintegration

In order to get the best possible value out of the substrates used, needs-oriented preparation in advance of the actual fermentation process is essential. Manure carrying a high proportion of straw-based litter or clusters of straw as an additional load can be crushed in preparation using a hammer mill to allow for liquid feeding of the reactor. This helps avoid problems related to mechanical "feeding". The downstream mixer is where "dry homogenisation" of the selected recipe of different types of poultry manure (chicken/turkey manure, dry chicken droppings/chopped straw) takes place. In the connected mixer pump, solid biomass is mashed with pre-warmed process water in accordance with the desired dry matter content. As poultry manure dissolves very well in the process liquid that is mixed in, the downstream two-shaft crusher has the task of macerating remaining fibres (straw/feathers) into particles with the largest possible surface. Within the liquid flow, the substrate reaches the hydrolysis chamber of the reactor in portions.

3. Biochemical disintegration

As everyone knows, the biogas process works in two steps, whereby acetogenesis and hydrolysis on the one hand and acetogenesis along with methanogenesis on the other hand each form a group: the hydrolysis step and the methanogenesis step. The bacteria in both steps have entirely different needs with regard to the milieu. Hydrolytically active bacteria are relatively strong, are characterised by short generation times and need a slightly acid pH value and oxygen. In addition, they are resistant to temperature fluctuations upon addition of fresh substrates.

Methane bacteria, on the other hand, are very sensitive! They react negatively to over-feeding with substrate structures that are difficult to digest. Temperature fluctuations caused by addition of cold or even frozen biomass as well as by input of oxygen along with the substrate have a restricting effect on the rate of multiplication.

Using the added oxygen, the upstream hydrolysis chamber of the reactor biochemically processes the pre-warmed substrate in such a way that the aforementioned problems can generally be avoided. For best results, the "feed" is therefore macerated and passed on to the methanogenesis step of the process in accurate doses. The disintegration facilitates increased volumetric load, with the aim of achieving a noticeable increase in yield.

4. Chamber-based gas production

With the GMS alpha process, the production of biogas takes place in the chamber-based reactor. The number of chambers depends on the planned output of the plant. Aside from the construction volume and energy requirement for substrate temperature control, the advantages of a compact chamber-based design lie principally in the ability to have a flexible process. The chambers can be run in parallel or in a row, whereby continuous or semi-continuous feeding is possible. Individual chambers can be disconnected and emptied as required without the whole plant having to be put on hold. The relatively small chamber volumes facilitate easy process monitoring.

5. Vertical mixing technology

All chambers in the reactor have a gas-tight concrete lid on which the mixer drivers are installed, featuring clear static and maintenance-related advantages. Vertical mixers with a special energy-saving blade construction transport the mixed product from the surface of the mixer shaft to the floor of the chamber. Upon rising, it is spread on the wall-based heating pipes of the chamber, ensuring even substrate temperature control. "Dead zones" of any kind are avoided using this mixing technology!

6. Sediment removal

The floors of the reactor chambers have diagonally placed slopes in the front corner of the chamber to act as deposit pits. The sediment that is deposited as part of the process is pushed into the pit through the stroke of the mixer. From there, it can be removed during continual operation.

7. Secondary fermentation with sediment removal

Practice has shown that sometimes sediment is only deposited when substrate particles have been largely consumed by the bacteria and a reduction in stirring intervals allows the particles to sink to the bottom of the tank. This is the case for both secondary fermentation and storage of fermentation residue. In order to combat this problem, the secondary fermentation tanks are fitted with conical bottoms and sand traps with discharge devices. This helps avoid the sediment building up until the plant is stopped.

8. No storage of fluid fermentation residue

GMS alpha plants have an extensive peripheral area for processing fermentation residue and therefore do not require any further storage of fluid fermentation residue. This advantage can be seen through savings made in investment and disposal costs. However, if the fermentation products are to be used as fertiliser in agriculture, this processing technology is not required. In this case, a sufficiently large fermentation residue storage facility must be provided instead.

9. Increase in cost effectiveness

The first step of fermentation product processing is separation into liquid and solid phases! The separated solid fermentation residue is dried as a raw material for further use as required.

Within the GMS alpha strip process ammonia is removed from the separated waste water, meaning that it can be fed back into the process as recyclate that is free from nitrogen loads.

As part of the GMS alpha strip process, "strong water", a 20-25% ammonia solution is produced. Ammonia solution is a versatile chemical that is common in industry and that has good marketing opportunities. In agriculture, ammonia water that has been very watered down can be used as a liquid nitrogen fertiliser.

By selling this product, the cost effectiveness of the GMS alpha plant can be sustainably increased.

10. Cost effectiveness

Despite the high standard of technology and extensive area around the plant (substrate/fermentation product processing), the investment costs for GMS alpha bio energy plants in terms of the amount of energy generated are considerably lower than for even traditional, simple plants!

Together with the right to claim remuneration under the EEG (German renewable energies act), affordable resources and the creation of value from fermentation end products, qualified operational management is almost guaranteed to lead to business success!