Feasibility Study for a Research Grade Anaerobic Digester at the Kellogg Biological Station Dairy

113 Pages·2012·3.24 MB·English

Feasibility Study for a Research Grade Anaerobic Digester at the
Kellogg Biological Station Dairy

Maria Melissa Rojas-Downing

Advisor
Dr. Tim Harrigan, MSU Biosystems and Agricultural Engineering

Report

August, 2012
Table of Contents
Introduction .............................................................................................................................................. 1
1. Anaerobic Digestion process ............................................................................................................. 5
1.1. Temperature ............................................................................................................................. 6
1.2. pH .............................................................................................................................................. 7
1.3. Retention Time .......................................................................................................................... 8
1.4. Solids concentration ................................................................................................................. 8
1.5. Nutrient requirements and Carbon/nitrogen ratio .................................................................. 9
1.6. Mixing of the digesting material ............................................................................................. 11
1.7. Food to microorganism ratio .................................................................................................. 11
2. Feedstock’s for Anaerobic Digester ................................................................................................ 12
2.1. Manure ......................................................................................................................................... 13
2.2. Agricultural Wastes ...................................................................................................................... 14
2.3. Urban waste ................................................................................................................................. 14
3. Byproducts ...................................................................................................................................... 15
3.1. Biogas ...................................................................................................................................... 15
3.2. Digestate ................................................................................................................................. 18
3.3. Reduce greenhouse gas emission ........................................................................................... 20
4. Types of Anaerobic Digester ........................................................................................................... 21
4.1. Plug Flow Digester ................................................................................................................... 22
4.2. Complete-mix Digester ........................................................................................................... 24
4.3. Covered Lagoon ...................................................................................................................... 26
3. Dairy Manure Digester .................................................................................................................... 27
3.1. Capital cost .............................................................................................................................. 34
4. Local regulations ............................................................................................................................. 43
4.1. Michigan permitting requirements ......................................................................................... 43
5. Michigan State University Kellogg Biological Station Dairy ............................................................ 44
6. Methodology ................................................................................................................................... 50
7. Results and Discussion .................................................................................................................... 53
8. Future Work .................................................................................................................................... 64
9. Addendum....................................................................................................................................... 67
9.1. Information collected at KBS Dairy ......................................................................................... 67
9.2. Information used for the Base farm confinement dairy ......................................................... 80
9.3. Output information from IFSM ............................................................................................... 89
Bibliography .............................................................................................................................................. 105
Summary
There is a need to develop Anaerobic Digester (AD) for small and medium size farms in the Great
Lakes Region, and KBS-MSU can provide leadership in the process through research, teaching and
outreach. These AD could be used for the treatment of Dairy farm waste, contributing with the
restructuration of the environment, reducing pollution such as greenhouse gas emission. The AD is
powered with organic matter waste (animal manure), the anaerobic bacteria will consume the waste
with the benefit of getting renewable energy through Biogas fuel, a rich fertilizer and reducing odors
associated with the land application of livestock waste.
Perhaps the greatest operational challenge at KBS is the variable and seasonal supply of
feedstock and an understanding of how to manage diverse feedstock in the AD process, because of the
pasture-based farm system. It is going to be done a feasibility study for the purpose of gathering the
initial information to assess the practicality and operational challenges of developing of a research grade
AD at KBS.
It is used a model called Integrated Farming Systems Model (IFSM) that evaluates the
environmental and economic impact, providing a desired level of farm production or profit and helping
to visualize in a better way if setting up an Anaerobic Digester in KBS Dairy is going to be feasible.
It will be modeled several scenarios for a comparison between them and analyze if introducing
an anaerobic digester at the KBS Dairy has a positive economically and environmentally impact or not.
For starting it will be modeled 4 scenarios with a farm that will represent small and medium farms from
Michigan State and it will be called “Base farm”, which are confinement dairy farms, with the variables:
small or large Holstein, and with or without AD. For analyzing the data, the different scenarios were
compared, calculating the difference between means.
The results shows that beside the Base Farm Confinement Dairy with Large Holstein had almost
4000 lb/cow of more milk production than the Base Farm Confinement Dairy with Small Holstein, the
total costs are higher, with $358,366 of difference and the total annual net emission of greenhouse
gases is 337,526 lb more in the dairy with Large Holstein. The housing facility is where it is produced
around 60% and 80% of the net emission of greenhouse gases of the base farms with AD and without
AD, respectively.
Labor cost, net feed and manure cost will increase if an AD is added to the farm system. In the other
side milking and animal handling energy cost; return to management and unpaid factors; total annual
methane in the farm; and total annual net greenhouse gas emission will decrease if an AD is added to
the farm system.
Introduction

There is always going to be waste as long as there is human life, because it is the
outcome of our needs of producing and consume foods. The concept of 4 R´s, which stands for
Reduce, Reuse, Recycle and Renewable energy, has been accepted as the principle of waste
handling.
An important percentage of the total waste is organic, such as sewage, animal
byproducts, and agricultural, industrial, and municipal solid waste ( Alternative fuels and
advanced vehicles data center, 2012), which also implies that they are biodegradable, and the
nature has its own solutions for this.
The scientists have evidence that the life in earth started 3.500 millions of years ago
with the development of the first microorganisms, when the oxygen didn’t even exist (Jeffares
& Poole, 2000). Life begins with bacteria’s called “anaerobic”. This bacteria has developed a
breathing mechanism that make them capable of consume organic matter without oxygen,
producing a mixture called biogas.
Biogas, also known as biomenthane, swamp gas, landfill gas, or digester gas is usually
50% to 80% methane and 20% to 50% carbon dioxide with traces of gases such as hydrogen,
carbon monoxide, and nitrogen ( Alternative fuels and advanced vehicles data center, 2012).
These anaerobic bacteria could be used for the treatment of our waste, contributing
with the restructuration of our environment. If provided a suitable location, which can be a
closed tank, called “Biodigester” and is powered with organic matter waste, this bacteria’s will
consume our waste with the benefit of getting energy through Biogas fuel.
Farm-scale digestion plants treating primarily animal wastes have seen widespread use
throughout the world. In rural communities small-scale units are typical; Nepal has some
50,000 digesters and China is estimated to have 8 million small-scale digesters. These digesters
are generally used for providing gas for cooking and lighting for a single household. In more
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developed countries, farm-scale Anaerobic Digester plants are generally larger and the gas is
used to generate heat and electricity (IEA Bioenergy, 2006).
Biogas recovery systems at livestock operations can produce renewable energy in cost-
effective ways. Animal manure can be collected and delivered to an anaerobic digester to
stabilize and optimize methane production.
The U.S. Environmental Protection Agency (EPA) estimates 8,200 U.S. dairy and swine
operations could support biogas recovery systems with the potential to generate more than 13
million megawatt-hours. Also Betts and Ling (2009) mentions that in 2007 the United States had
9.158 million milk cows on 71,510 operations. These cows produced 185.6 billion pounds of
milk along with an estimated 500 billion pounds of manure. This byproduct of milk production
is routinely handled by collecting it, storing it, and spreading it over the land. In the beginning
of the 21st century, the convergence of a number of factors, including the changing structure of
milk production, the shrinking local land base on which to spread dairy manure, environmental
issues, and rising energy costs accompanied by a focus on renewable energy, have heightened
interest in alternative methods for handling dairy manure (Betts & Ling, 2009).
The Anaerobic Digester (AD) also allows compost and nutrient recovery. The byproduct
of biodigesters is a high quality organic fertilizer that can be used in agricultural systems and
odors associated with the land application of livestock waste are greatly reduced. Most dairies
that own or contribute manure to biodigesters use the liquid effluent on their own fields (Lake-
Brown, 2012).
In Figure 1 is presented the inputs and outputs of the AD that has been mentioned
before.
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Figure 1. Inputs and outputs of the Anaerobic Digester
Anaerobic Digester (AD) not only provides energy and compost and nutrient recovery,
but also allows pollution prevention. The emission of CO and other greenhouse gases (GHG)
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has become an important issue, particularly since Russia has ratified the Kyoto Protocol which
came into force on 16 February, 2005. Governments and industries are therefore increasingly
on the lookout for technologies that will allow for more efficient and cost-effective waste
treatment while minimizing GHG. The CO -trade will even further increase the need for CO -
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neutral technologies (IEA Bioenergy, 2006).
In addition, anaerobic digestion kills several pathogens, and effectively reduces
biological oxygen demand (BOD) and chemical oxygen demand (COD) present in waste, which
protects groundwater when the effluent is land applied (EPA, 2005).
The use of this technology has been increasingly attractive for manure management,
most of all because of the new laws regulating odor, groundwater contamination, and
greenhouse gases in various parts of the United States (Simpkins, 2005). IEA Bioenergy (2006)
presents a summary of the benefits resulting from the use of the Anaerobic Digester (Table 1).

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Table 1. Benefits resulting from the use of the Anaerobic Digester
Benefits
Waste  Natural waste treatment process
 Requires less land than aerobic composting
Treatment
 Reduces disposed waste volume and weight to be landfilled
Energy  Net energy producing process
 Generates high quality renewable fuel
 Biogas proven in numerous end-use applications
Environmental  Significantly reduces greenhouse gas emissions
 Eliminates odors
 Produces a sanitized compost and nutrient-rich liquid fertilizer
 Maximizes recycling benefits
Economic Considering the whole life-cycle, it is more cost-effective than other
treatment options
Source: Bioenergy (2006)
Also Burke (2001) provides additional benefits on the economic side, such as:
 The time devoted to moving, handling, and processing manure is minimized.
 Biogas is produced for heat or electrical power.
 Waste heat can be used to meet the heating and cooling requirements of the dairy.
 Concentrating nutrients to a relatively small volume for export from the site can reduce
the land required for liquid waste application.
 The rich fertilizer can be produced for sale to the public, nurseries, or other crop
producers.
 Income can be obtained from the processing of imported wastes (tipping fees), the sale
of organic nutrients, greenhouse gas credits, and the sale of power.
 Power tax credits may be available for each kWh of power produced.
 Greenhouse tax credits may become available for each ton of carbon recycled.
 Finally the power generated is “distributed power” which minimizes the need to modify
the power grid. The impact of new power on the power grid is minimized.
Looking to all the benefits resulting from the use of an AD that is why it’s going to be
done a feasibility study for a research grade Anaerobic Digester at the Kellogg Biological Station
(KBS) Dairy. The feasibility study will determine if it is:
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a. technically feasible
b. is feasible within the estimated cost and
c. will be profitable.
Additional skills supporting the economic feasibility of a digester include marketing and
negotiation (for energy and other byproduct sales), engine maintenance and repair (to keep
operating expenses low when utilizing the biogas for heat and/or energy), and innovation
(finding uses for the byproducts and effectively implementing them) (Betts & Ling, 2009).
The aim of the feasibility study is to provide facts and figures for decision markers in KBS
to support the development of the economically and environmentally most promising biogas
technology on-farm.
It is also important to take into account that the decision to install a digester is
dependent upon the policies of the local utility, local regulations, local fuel and electricity rates,
access to grants and financing, and the operator's knowledge, skill, and level of risk aversion
(Betts & Ling, 2009). The challenges to adoption include:
 Electricity rates and interconnection issues
 System design flaws
 The limited number of digester providers and lack of information
 Additional time and skill required to manage the digester adequately
 The lack of ability to capture value from byproduct use or sale
 Difficulties in obtaining financing and/or funding

1. Anaerobic Digestion process
The AD process occurs naturally in the bottom sediments of lakes and ponds, in swamps,
peat bogs, intestines, and even in hot springs. It is a complex process that occurs mainly in
three stages. In the first stage a group of microorganisms converts organic material to a form
that a second group of organisms uses. In the second stage the second group of organisms form
organic acids. And in the last stage Methane-producing (methanogenic) anaerobic bacteria use
these acids and complete the decomposition process (U.S Department of Energy, 2012).
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Gerardi (2003) also describes these three stages as: Hydrolysis, acid production, and
methane production. In the first stage, hydrolytic bacteria break down complex carbohydrates,
lipids, and protein into simple sugars, fatty acids, and amino acids, respectively. In the second
stage, simple substrates produced in hydrolysis are then processed into organic acids
(primarily acetate) and alcohols. And in the last stage, methanogenic, or methane producing
microorganisms convert organic acids and alcohols into carbon dioxide and methane.
So there are two kinds of bacteria needed for anaerobic digesters to function properly.
First the fermenting bacteria those are the ones that feed off the manure or other organic
materials and release organic acids, and the Methanogenic bacteria, the one that also feeds on
the organic matter, and emits methane as a waste (Simpkins, 2005).
The output of anaerobic digestion is biogas which is available to heat the digester and
potentially satisfy other farm energy needs and digestate, which, if desired, is divided into solid
and liquid components using a separator, and could be use as a fertilizer (Burke 2001).
There are several factors that can affect the rate of digestion and biogas production,
such as: pH, retention time, solids concentration, nutrient requirements and carbon/nitrogen
ratio, food to microorganism ratio, mixing of the digesting material, the particle size of the
material being digested and the most important temperature.
1.1. Temperature

The U.S Department of Energy (2012) mentions that the anaerobic bacteria
communities can endure temperatures from below freezing to more than 57.2°C . Because of
the widespread natural occurrence of methane bacteria the IEA Bioenergy (2006) demonstrates
that anaerobic degradation can take place over a wide temperature range from 10°C to over
100°C and at a variety of moisture contents from around 50% to more than 99%. But they
thrive best at temperatures of about 36.7°C (mesophilic) and 54.4°C (thermophilic). Bacteria
activity, and thus biogas production, falls off significantly between about 39.4°C and 51.7°C and
gradually from 35°C to 0°C (U.S Department of Energy, 2012).
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