Anaerobic digester instability: symptoms, causes and prevention
An unstable digester is one that has lost the balance between the bacteria that produce acids and the archaea that produce methane. The symptoms appear in a predictable order: first the propionic acid and the FOS/TAC ratio rise, then biogas production falls and the pH drops; if nothing is done, the reactor acidifies and collapses. […]
How to add a new substrate to the anaerobic digester (biogas): step-by-step protocol
Adding a new substrate to the digester is one of the highest-risk moments of a biogas plant: done badly, it acidifies the reactor in days. The safe protocol has five steps: characterise the substrate (VS, C/N, BMP, inhibitors), run a preliminary test, add it with a gradual ramp (0.2-0.5 kg VS/m³·day per week, starting below […]
Biogas process engineering: what it is and why it decides your plant’s performance
Biogas process engineering is the discipline that designs and optimises what happens inside the digester: the biology and the process conditions (substrates, load, retention time, temperature, control), not the civil works or the mechanics. It is what decides whether a plant delivers 100 % of its potential or stays at 70 %. Unlike EPC engineering, […]
Enzymes, micronutrients, bioaugmentation and nanoparticles in biogas: when they really work
There are three big families of biological additives for biogas: micronutrients or trace elements (Ni, Co, Fe, Se, Mo), enzymes and bioaugmentation (adding microorganisms). A fourth, more recent route is added to them: conductive nanoparticles. They are not magic solutions, but they are not smoke either: each one solves a specific problem and only helps […]
Biogas composition: CH4, CO2, H2S and minor compounds
Biogas is a gaseous mixture dominated by methane (50-65 %) and CO₂ (35-45 %), with a handful of minor components that decide its quality and treatment cost: H₂S (50-6,000 ppmv), ammonia, siloxanes, VOCs, water vapour and traces. Methane is the energy; the rest are problems to manage. Its calorific value is around 6 kWh/Nm³ at […]
Anaerobic co-digestion: fundamentals, benefits and mixture design
Anaerobic co-digestion means digesting two or more substrates at the same time in the same reactor instead of just one. Well designed, it balances the digester’s diet: one substrate provides what the other lacks (carbon, nitrogen, moisture, micronutrients), which stabilises the process and raises methane production by 15-30 % compared with mono-digestion. The key lies […]
Types of anaerobic digesters: CSTR, UASB, plug-flow and hybrid configurations
There is no universal digester: the right configuration depends on the substrate, the scale and the objective. CSTR reactors (fully mixed) are the standard for agro-industrial and livestock waste; UASB reactors treat industrial wastewater at high speed; plug-flow reactors suit very solid substrates; covered lagoons are the low-cost, high-volume option; two-stage configurations separate phases for […]
What is anaerobic digestion: fundamentals, phases and applications
Anaerobic digestion is a biological process in which a consortium of microorganisms breaks down organic matter in the absence of oxygen and generates two valuable products: biogas (a methane-rich mixture) and digestate (an organic fertiliser). It happens in four linked phases (hydrolysis, acidogenesis, acetogenesis and methanogenesis) and needs controlled conditions of temperature, pH and nutrients. […]
Biogas sample traceability: the lab-plant chain of custody
Biogas sample traceability is what separates a useful figure from a worthless number. A poorly taken, poorly preserved or poorly labelled sample gives results that look real but are not, and wrong decisions are made on them. FOS/TAC degrades in under 24 hours and VFAs in hours. Without a cold chain, labelling and records, the […]
Biomethane EN 16723: quality for grid injection
Biomethane EN 16723 is biogas purified to natural-gas quality for injection into the grid. The standard sets strict limits: methane above 96%, oxygen below 1% and traces of H2S, siloxanes and water reduced to a minimum. Reaching them is not only a matter of the upgrading equipment: biomethane quality starts in the digester. The dirtier […]