# Low-Cost IoT-Based Computational System for Real-Time Biogas Monitoring in UASB Reactors Using NDIR Sensors and ESP32

## TL;DR

This paper introduces a low-cost IoT system for real-time biogas monitoring in UASB reactors using NDIR sensors and ESP32, enabling remote tracking of methane and flow rates.

## Contribution

A modular, fault-tolerant IoT system for real-time, low-cost biogas monitoring in UASB reactors using NDIR sensors and ESP32.

## Key findings

- The system achieved stable data transmission with an average latency of ∼1.77 seconds over 30 days.
- Measured methane ranged from 53.31–88.0%, and flow rates from 42.84–76.16 NL·d–1 with high accuracy.
- The system demonstrated near-zero sensor drift and strong temporal agreement with measured data.

## Abstract

UASB reactors are
widely employed in wastewater treatment due to
their operational simplicity and the potential for energy recovery
from biogas, although continuous, low-cost monitoring of CH4 and flow rate remains challenging. This work presents the development
and validation of an IoT system for remote, real-time monitoring,
integrating NDIR sensors for CH4/CO2, a temperature
sensor, a pressure sensor, a thermal mass flow meter, and an ESP32
platform with web/mobile interfaces. Deployment was carried out in
a bench-scale UASB reactor treating an industrial slaughterhouse effluent.
Over 30 days of continuous operation, stable data transmission was
recorded with an average latency of ∼1.77 s; measurements covered
42.84–76.16 NL·d–1 (flow) and 53.31–88.0%
(CH4), with temperature within a narrow mesophilic range
(22.25–27.80 °C) and near-zero sensor drift. Estimates
based on removed chemical oxygen demand (COD), normalized to STP,
yielded 45.18–74.72 NL·d–1 (flow). Temporal
agreement with the measured series was observed (MAE = 6.58 NL·d–1 and 4.69 percentage points; MAPE = 9.88% and 6.69%
for flow and composition, respectively). This modular, fault-tolerant
architecture demonstrates feasibility for supporting operational control
and assessing the methane energy potential in decentralized applications.