Q:

What is the size and material of bioreactors?

Our reactor is a standardized 1 liter wide-mouth HDPE bottle that can handle more substrates and inoculums. This improvement reduces possible errors in the experiment. HPDE is biologically inert and can remain stable at 100°C.

Q:

What is the allowed (or suggested) minimal volume of digestate in 1L bioreactors?...

We use 650-700 ml of inoculum + sample in the 1 litre reactor bottles. With this volume, the test ports are below the liquid level and we can syringe out samples for analysis without having to lose biogas. However, if you want to use smaller sample volumes you can do so using the same 1 litre bottles.

Q:

How many ports are available for sampling?

There is an access test tube provided on the reactor head which goes below the liquid level. This allows you to syringe out sample for analysis and also to measure pH without losing biogas. The pH and redox potential are not monitored continuously by our Arduino system. You can use a hand held pH meter with 6 mm pH probe to measure the pH. Apart from the test port and an in use biogas port, we have two additional gas ports that can be used for flushing the reactor headspace. Any bespoke ports required will incur additional charge.

Q:

How can gas samples be taken for subsequent GC analysis?

You can analyse the biogas composition using Tedlar gas bags attached at the outlet. Our gas flow meters have individual chambers for each reactor. The gas from the bioreactors enters the gas flow meter from the bottom and bubbles through the water to fill a vessel. As the vessel fills, it floats then tumbles and this triggers the logging of the occurrence and the storage of the temperature and pressure at each occurrence. After the tipping, the gas is evacuated to the headspace of the gas flow meters. Each headspace has a hose tail fitting where a Tedlar gas bag of 5 litres or 10 litres can be fitted to collect the biogas after measuring gas flow. The biogas composition collected in the gasbags can be analysed using GC or a portable gas analyser. The other way to do it is to fill the gas flow meter with caustic solution instead of water. The caustic solution scrubs out the carbon dioxide as the gas enters the gas flow meter from the bottom and you will be measuring methane flow instead of biogas flow. We recommend using the first method as it gives flexibility to measure the Methane, ...

Q:

How are the reactors mixed?

All reactors are mixed at exactly the same speed through stainless/silicone paddles driven by a gearbox. One motor for 15 reactors. Stainless steel/silicone paddles deliver consistent mixing to all digesters in each set. Most commercially-available BMP sets do not guarantee equal mixing for all reactors in the set. Some rely on daily manual shaking, shaking surfaces, magnetic stirrers, etc., which is ok for absolute values of BMP but limits the use of kinetic data for rapid evaluation of inhibition or of the effect of feedstock composition on dynamics of biogas production If needed, the mixing can be controlled by a commercial timer to come on and off at the set timings....

Q:

How is the temperature controlled?

The temperature of operation is controlled by immersion of reactors in a Grants © water bath up to 95ºC with 0.5º C setting resolution. A lid that holds the reactors in place has been designed to minimise the loss of bath water by evaporation, facilitating tests at thermophilic temperatures without the common issues of water evaporation when operating water baths at thermophilic temperature.

Q:

How is the data recorded?

The main data logging software is stored on the Arduino monitor which is integrated at the end of the gas flow meter. There are three utilities which run on a laptop that is connected to the Arduino over USB. These utilities are ‘startrun‘ - which is used to transfer basic experimental data to the Arduino at commencement of a run, ‘filegrab‘ - which is used to transfer the log files built up by the Arduino back to the laptop and ‘monitor‘ - which provides a simple monitoring facility. Results are written to a number of .csv log files which can be opened with Excel or similar. These files are held on a microSD card which is part of the Arduino system and can be uploaded to the laptop at any time and as often as required (eg daily) using the filegrab utility. The gas flow meter automatically logs the final gas yield results in ml/day or ml/g VS and compensates to standard temperature and pressure (STP) automatically in real time. The results can be obtained using the ‘Filegrab‘ utility on the laptop. ...

Q:

What is the minimal computer configuration to support the Arduino software?

A computer or laptop with Windows 10 with a spare USB port – can be a 32 bit machine or a 64 bit machine – software supports both.

Q:

How is the cleaning of the gasflowmeter?

Some user dose algaecide into the gas flow meters. Prepare a solution of bleach and fill the gas flow meter with it leaving it soaking overnight. Then, shake the gas flow meter gently and flush connecting a water hose at gentle rate for a few minutes. This will not leave the gas flow meter sparking clean, but it will be clearer. If the film is firmly attached, then you might need to remove the top lid and with a bleach solution brush the buckets. The ultimate wash would be to remove the tumbler buckets and give the machine a thorough clean.