Our BMP/RBP machines have been developed based on operational research in the UK food waste industry. Results with the equipment available at the time were not consistent enough for the heterogeneous feedstock used due to issues with mixing consistency, sample size, and error in gas flow measurement. Also, for practical application, it was important to do as little pre-processing as possible to better translate results for operational decisions. Through hundreds of tests done by ourselves, and thousands of tests by our clients, our machines have been thoroughly evaluated for practicality, results quality, and durability (NRM alone has 26 of our Nautilus machines and ATL has 8 Nautilus machines doing certified RBP tests non-stop in the UK).

 

Before developing our machine, we used reactors with individual mixer motors and found that, although the final biogas yield after 30 days was similar, small changes in mixer speed, or a mixer motor failing impacted the kinetics of the biogas production for individual samples, impacting the confidence on results. If the test is to be used as an indicator of treatability, or to help identify the inhibition potential or refractory behaviour of feedstock entering AD plant, mixing all reactors at the same frequency and intensity is paramount; for example to measure consistently lag periods. For BMP/RBP tests it is important to maintain mechanical and thermal conditions as consistent as possible in all the 15 reactors in a machine. Anaero Technology developed and gained a patent for a gearbox mixer system that, through one motor alone, mixes all 15 reactors at the same speed

 

We have been asked for smaller BMP reactor size but avoided them due to the negative impact of smaller sample size on test error potential through handling issues and less biogas production. The less gas that is measured in a test, the larger the error caused from missing the odd bubbles during measurement. For this reason, our BMP reactors are 1 litre wide mouth HDPE bottles. 

 

Wide mouth bottles allow easier inoculum and sample handling, and easy to handle reactor caps have long narrow necks to ease the handling of bottles and for improved gas-tightness. Finally, after long evaluation, we opted for standard HDPE bottles that can be used several times and replaced at low cost. Even if a bottle drops to the floor it will not break. Our BMP/RBP reactors can be fitted with optional access ports to enable gas-tight sampling and/or pH measurement during tests

 

Each machine has a gas flow meter, and individual cells measure flow and isolate the gas of each reactor if sampling is required. This enables users to either fill the flow meter with caustic soda solution to measure methane only, or fit standard scrubber bottles between the reactors and the gas flow meters (we can supply them in addition or clients who require this often have their own). Our preferred method is to fill gas flow meters with water, can be acidified, and collect gas in gas bags for analysis, calculating headspace dilution. This is useful for AD operators since H2S is a nuisance gas that requires cleaning for biogas use, and its presence can indicate nuisance potential of digestate. Thus, identifying feedstock causing high H2S concentrations is economically important.

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BMP Features

Fast Assembly

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Gasflow Meter

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Fast test set up

Minimum Water Evaporation

Easy Sample Handling

  • All you need is small beakers, spatulas or spoons, or syringes, a good scale, and a calculator.

  • Wide mouth facilitates pouring of samples of all rheology into the reactors with no bits left stuck to reactor walls.

  • Use long reactor cap neck to easily move reactors to place of use and start test.

Consistent

Bespoke Software

BMP Features

Fast test set up

  • Check flow meter calibration and measure inoculum and sample volatile solids.

  • Accurately load reactors with target inoculum and sample. Wide mouth makes this easy.

 

  • Fit reactor tops and place them in the water bath. Fit water bath lid and line gearbox on reactors.

 

  • Connect gas flow meter hose to selected reactors. Flush gas if required.

 

  • Switch bath on and set temperature. Switch mixer motor on and ensure all mixers engaged.

Easy Sample Handling

  • All you need is small beakers, spatulas or spoons, or syringes, a good scale, and a calculator.

  • Wide mouth facilitates pouring of samples of all rheology into the reactors with no bits left stuck to reactor walls.

  • Use long reactor cap neck to easily move reactors to place of use and start test.

Minimum Water Evaporation

  • We design our BMP machine based on widely available HDPE bottles to minimise replacement cost and maximise active volume for more accurate testing.

  • Bath Perspex lids are designed to stop water vapour escaping through spaces. Vapour condenses on lids and falls back in the bath.

  • Low water loss even in thermophilic operation.

Consistent

Biological tests using heterogeneous inoculum and samples present small differences in gas production. However, the minimising potential physical differences, such as temperature and mixing helps improve consistency between sample sets.

For a same substrate, assuming full homogenisation, and assuming homogenised inoculum in all reactors, the main parameters to control to have lower kinetic differences are temperature and mixing. Good quality water baths assure minimum differences in temperature, even if un-stirred.

Anaero Technology minimises differences in mixture intensity by mixing all the reactors in a bath through a gearbox that uses only one motor. This also reduces replacement costs by having only one readily available motor to service.

Bespoke Software

The Arduino based system consists of an Arduino 2560 Mega microcontroller which acts as the main controller for the data logger. When one of the tumblers in the gas flow meter tips, a magnet attached to the tumbler bucket causes the reed switch to close and record the volume.  As each tumbler event is captured it is possible to guarantee that all tumbler events are registered, even if the Arduino is busy transferring files or performing other calculations at the time of the event.  Also connected to the Arduino are  BMP280 barometric pressure sensor, a microSD card reader,  and a thermocouple amplifier to which is connected a type-K thermocouple.  All tumbler events are written to a log file on the microSD card including the channel number, the time at which the event occurred, the air pressure at that time and the temperature as recorded by the thermocouple. For ease of use, other log files (e.g a summary of what has happened in the last 24 hours) which are calculated from this event data, are also stored on the memory card. A suite of Python utilities has also been developed to simplify set up and operation of the data logger.

Biological tests using heterogeneous inoculum and samples present small differences in gas production. However, the minimising potential physical differences, such as temperature and mixing helps improve consistency between sample sets. For a same substrate, assuming full homogenisation, and assuming homogenised inoculum in all reactors, the main parameters to control to have lower kinetic differences are temperature and mixing. Good quality water baths assure minimum differences in temperature, even if un-stirred. Anaero Technology minimises differences in mixture intensity by mixing all the reactors in a bath through a gearbox that uses only one motor. This also reduces replacement costs by having only one readily available motor to service.

The Nautilus model is our standard BMP/RBP design to measure the biogas potential of samples from the most dilute to solid. It has even been adapted to replicate dynamics in landfills by researchers in Wales!

 

It has 15 x 1 litre HDPE reactors immersed in a water bath and mixed in total synchrony with a patented gearbox. Temperature and mixing conditions are the same for all reactors in a set. The 1 litre reactor volume allows larger sample and inoculum volumes to be processed, reducing the margin of error. 

 

The Nautilus model provides access to reactors via optional air-tight ports that enable pH monitoring, nutrient supplementation, or sampling without disruption to batch tests. You can also fir extra ports to flush reactors with biogas or nitrogen at the start of the test.

 

We have recently introduce silicone mixer blades to reduce the rigidity of steel blades and allow thorough mixing, even in high solids conditions in the digester without putting excessive loads on the mixer motor.

 

All our batch sets include gas flow meters with real-time conversion to standard temperature and pressure. All raw and processed gas flow data can be downloaded in csv format and readily converted to graphs, or exported for specific mathematical analysis.

 

Our machines provide high quality analytical results at reasonable price, broadening access to top rate equipment for researchers.

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