Landfilling of Waste

Biogas

T.H. Christensen, R. Cossu, R. Stegmann, T.H. Christensen, R. Cossu, R. Stegmann

• Publisher: CRC Press
• Year: 2020
• Topic: Technology & Engineering
• eBook ISBN:
  9781000143898
• Subtopic: Modern History
• Index: Technology & Engineering

Landfilling of Waste: Biogas is the third in a series of reference books which provide a comprehensive overview of the state of the art and identify new directions in landfill technology and landfill research. As well as describing gas generation and composition, the book covers the environmental aspects, discusses gas production, extraction and transportation, treatment and utilization, emissions and safety, and ends with a selection of case studies.

1. INTRODUCTION

1.1 Gas Issues in Landfill Management

THOMAS H. CHRISTENSEN^a, RAFFAELLO COSSU^b & RAINER STEGMANN^c
aInstitute of Environmental Science and Engineering, Technical University of Denmark, Building 115, DK-2800 Lyngby, Denmark
^bDIGITA, Department of Geoengineering and Environmental Technologies, University of Cagliari, Piazza d'Armi, 1-09123 Cagliari, Italy
^cInstitute of Waste Management, Technical University of Hamburg-Harburg, Harburger Schlossstrasse 37, D-21071 Hamburg, Germany

INTRODUCTION

Landfill plays a most important role in the framework of solid waste disposal and will remain an integral part of the new strategies based on integrated solid waste management. Landfill design concepts are mainly devoted towards ensuring minimal environmental impact in accordance with observations made concerning old landfills, but in recent years landfill design usually also includes facilities for controlling gas migration and utilization of the energy associated with the biogas.

Gas generated in the landfill (LFG) is a result of a mass transfer process. Waste entering the landfill undergoes biological, chemical and physical transformation governing the relationship between the solid phase (the waste), the liquid phase (leachate) and the gas phase. The main components of the landfill gas (CH₄, CO₂) are a result of biological processes, while the trace components, which are numerous, are generated by biological processes as well as by volatilization. Gas in landfills has existed as long as landfills have existed, but the realization of landfill gas causing problems to the environment is relatively recent.

HISTORY

For a long time, people working on landfills knew that gas is inside a landfill. This could be proven by simply pushing a steel pipe into the landfill and lighting the open end of the pipe. The flame may burn over long time until blown out by the wind.

Migration of gas into the surrounding areas was observed in terms of dying trees and mal-growth of crops on agricultural fields. This was seen in particular at landfills located in gravel pits. Explosions occurred, where gas accumulated in buildings and manholes in or adjacent to the landfills and was ignited by the use of open fires or electrical sparks.

Landfill gas control started in the late 1960s and early 1970s in the USA, where huge landfills had been created. The first plant in Europe came into operation in Germany in the mid-1970s, incorporating a great deal of experience gained in the USA. Later, LFG technology spread all over Europe and into other countries.

In Germany, gas utilization focused from the beginning on direct thermal utilization (e.g. in industry) and electricity production using gas engines. These were, in general, Otto engines that were developed for natural gas. By contrast, in the USA LFG was at first upgraded to natural gas quality by removing CO₂. Substantial experience has been gained since then. LFG plant operators had to face severe corrosion problems e.g. in the gas pretreatment plants for CO₂ removal in the USA and in gas engines in Germany. In addition, it was found out that there are a great number of organic trace components in LFG that are responsible for these corrosion problems. At first, no explosion control standards existed, and the emissions from thermal treatment plants were unknown. With time, more and more regulations were made regarding the planning, construction and operation of LFG extraction and utilization plants. This also influenced the economy of gas utilization. While in the USA, in the early days, LFG utilization had been seen as a big business (there was a big run on the gas utilization rights at large landfills), this has changed with time. In Germany the main emphasis for LFG utilization was also commercial, until it was realized that no big profits (if any) could be made. The economics of LFG utilization are of course also closely linked to energy prices.

The reasons for LFG abstraction and utilization changed. While in some states in the USA gas abstraction was done to control releases of the carcinogenic trace component vinyl chloride, explosion control and vegetation protection became more and more relevant in other countries. Today also the contribution of LFG emissions to the greenhouse effect is a reason in many countries that LFG extraction and utilization plants are mandatory at all new landfills.

Landfill gas technology initially was developed by pioneers: people who operated a landfill and who became enthusiastic about LFG. The scientific investigations followed with a certain time lag. Today, LFG technology is a proven technology, but many a lesson has been learned in the past. This book offers a comprehensive state of the art of landfill gas and its utilization.

There are still areas in this field where scientific and practical experiences are at a low level. This is the case, for example, for the prediction of long-term gas production in combination with active extraction, the effects of different kinds of surface liners on the LFG recovery rate, the extraction of LFG at small and old landfills, and the use of biofilters for the treatment of LFG at low rates. Also a new, but not yet proven, technology with artificial aeration of old landfills must be closely studied.

GAS CONTROL STRATEGIES

Gas control strategies may involve control of the waste input, control of the landfill reactor, and control of gas discharges to the environment.

Control of Waste Input

The first step in the waste input control strategy should be that of reducing to a min...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Contents
• Preface
• List of Contributors
• 1 INTRODUCTION
• 2 GAS GENERATION AND COMPOSITION
• 3 ENVIRONMENTAL ASPECTS
• 4 GAS PRODUCTION
• 5 EXTRACTION AND TRANSPORTATION
• 6 GAS TREATMENT
• 7 GAS UTILIZATION
• 8 GAS MIGRATION, EMISSIONS AND SAFETY ASPECTS
• 9 CASE STUDIES
• Index