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A new concept known as “hydraulic fracturing “ to enhance the recovery of land fill gas from new and existing land fill sites have been tested jointly by a Dutch and  Canadian companies. They claim it is now possible to recover such gas economically and liquefy them into Bio-LNG to be used as a fuel for vehicles and to generate power.

Most biofuels around the world are now made from energy crops like wheat, maize, palm oil, rapeseed oil etc and only  a minor part is  made from waste. But such a practice in not sustainable in the long run considering the anticipated food shortage due to climate changes.   The EU wants to ban biofuels that use too much agricultural land and encourage production of biofuels that do not use food material but waste materials. Therefore there is a need to collect methane gas that is emitted by land fill sites more efficiently and economically and to compete with fossil fuels.

There are about 150,000 landfills in Europe with about 3–5 trillion cubic meters of waste (Haskoning 2011). All landfills emit landfill gas; the contribution of methane emissions from landfills is estimated to be between 30 and 70 million tons each year. Landfills contributed an estimated 450 to 650 billion cubic feet of methane per year (in 2000) in the USA. One can either flare landfill gas or make electricity with landfill gas. But it is prudent to produce the cleanest and cheapest liquid biofuel namely “Bio-LNG”.

Landfill gas generation: how do these bugs do their work?

Researchers had a hard time figuring out why landfills do not start out as a friendly environment for the organisms that produce methane. Now new research from North Carolina State University points to one species of microbe that is paving the way for other methane producers. The starting bug has been found. That opens the door to engineer better landfills with better production management. One can imagine a landfill with real economic prospects other than getting the trash out of sight. The NCSU researchers found that an anaerobic bacterium called Methanosarcina barkeri appears to be the key microbe. The following steps are involved in the formation of landfill gas is shown in the diagram

Phase 1: oxygen disappears, and nitrogen

Phase 2: hydrogen is produced and CO2 production increases rapidly.

Phase 3: methane production rises and CO2 production decreases.

Phase 4: methane production can rise till 60%.

Phases 1-3 typically last for 5-7 years.

Phase 4 can continue for decades, rate of decline depending on content.

Installation of landfill gas collection system

A quantity of wells is drilled; the wells are (inter) connected with a pipeline system. Gas is guided from the wells to a facility, where it is flared or burnt to generate electricity. A biogas engine exhibits 30-40% efficiency. Landfills often lack access to the grid and there is usually no use for the heat.

The alternative: make bio-LNG instead and transport the bio-LNG for use in heavy-duty vehicles and ships or applications where you can use all electricity and heat.

Bio-LNG: what is it?

Bio-LNG is liquid bio-methane (also: LBM). It is made from biogas. Biogas is produced by anaerobic digestion. All organic waste can rot and can produce biogas, the bacteria does the work. Therefore biogas is the cheapest and cleanest biofuel  that can be generated without competing  with food or land use. For the first time there is a biofuel, bio-LNG, a better quality fuel than fossil fuel.

The bio-LNG production process

Landfill gas is produced by anaerobic fermentation in the landfill. The aim is to produce a constant flow of biogas with high methane content. The biogas must be upgraded, i.e. removal of H2S, CO2 and trace elements;

In landfills also siloxanes, nitrogen and Cl/F gases. The bio-methane must be purified (maximum 25/50ppm CO2, no water) to prepare for liquefaction. The cold box liquefies pure biomethane to bio-LNG

Small scale bio-LNG production using smarter methods.

•Use upgrading modules that do not cost much energy.

•Membranes which can upgrade to 98-99.5 % methane are suitable.

•Use a method for advanced upgrading that is low on energy demand.

•Use a fluid / solid that is allowed to be dumped at the site.

•Use cold boxes that are easy to install and low on power demand.

•Use LNG tank trucks as storage and distribution units.

•See if co-produced CO2 can be sold and used in greenhouses or elsewhere.

•Look carefully at the history and present status of the landfill.

What was holding back more projects?

Most flows of landfill gas are small (hundreds of Nm3/hour), so economy of scale is generally not favorable. Technology in upgrading and liquefaction has evolved, but the investments for small flows during decades cannot be paid back.

Now there is a solution: enhanced gas recovery by hydraulic fracturing. Holland Innovation Team and Fracrite Environmental Ltd. (Canada) has developed a method to increase gas extraction from landfill 3-5 times.

Hydraulic fracturing increases landfill gas yield and therefore economy of scale for bio-LNG production

The method consists of a set of drilling from which at certain dept the landfill is hydraulically broken. This means a set of circular horizontal fractures are created from the well at preferred depths. Sand or other materials are injected into the fractures. Gas gathers from below in the created interlayer and flows into the drilled well. In this way a “guiding” circuit for landfill gas is created. With a 3-5 fold quantity of gas, economy of scale for bio-LNG production will be reached rapidly. Considering the multitude of landfills worldwide this hydraulic fracturing method in combination with containerized upgrading and liquefaction units offers huge potential. The method is cost effective, especially at virgin landfills, but also at landfill with decreasing amounts of landfill gas.

Landfill gas fracturing pilot (2009).

• Landfill operational from 1961-2005

• 3 gas turbines, only 1 or 2 in operation at any time due to low gas extraction rates

• Only 12 of 60 landfill gas extraction wells still producing methane

• Objective of pilot was to assess whether fracturing would enhance methane extraction rates

Field program and preliminary result

Two new wells drilled into municipal wastes and fractured (FW60, FW61). Sand Fractures at 6, 8, 10, 12 m depth in wastes with a fracture radius of 6 m. Balance gases believed to be due to oxygenation effects during leachate and

Groundwater pumping.

Note: this is entirely different from deep fracking in case of shale gas!

Conceptual Bioreactor Design

 The conceptual design is shown in the figures.There are anaerobic conditions below the groundwater table, but permeability decreases because of compaction of the waste. Permeability increases after fracking and so does the quantity of landfill gas and leachate.

Using the leachate by injecting this above the groundwater table will introduce anaerobic conditions in an area where up till then oxygen prevailed and so prevented landfill gas formation

It can also be done in such a systematic way, that all leachate which is extracted, will be disposed off in the shallow surrounding wells above the groundwater table.

One well below the groundwater table is fracked, the leachate is injected at the corners of a square around the deeper well. Sewage sludge and bacteria can be added to increase yield further

Improving the business case further

A 3-5 fold increased biogas flow will improve the business case due to increasing

Economy of scale. The method will also improve landfill quality and prepare the landfill for other uses.

When the landfill gas stream dries up after 5 years or so, the next landfill can be served by relocating the containerized modules (cold boxes and upgrading modules). The company is upgrading with a new method developed in-house, and improving landfill gas yield by fracking with smart materials. EC recommendations to count land fill gas quadrupled for renewable fuels target and the superior footprint of bio-LNG production from landfills are beneficial for immediate start-ups

Conclusions and recommendations

Landfills emit landfill gas. Landfill gas is a good source for production of bio-LNG. Upgrading and liquefaction techniques are developing fast and decreasing in price. Hydraulic fracturing can improve landfill gas yield such that economy of scale is reached sooner. Hydraulic fracturing can also introduce anaerobic conditions by injecting leachate, sewage sludge and bacteria above the groundwater table. The concept is optimized to extract most of the landfill gas in a period of five years and upgrade and liquefy this to bio-LNG in containerized modules.

Holland Innovation Team and Fracrite aim at a production price of less than €0.40 per kilo (€400/ton) of bio-LNG, which is now equivalent to LNG fossil prices in Europe and considerably lower than LNG prices in Asia, with a payback time of only a few years.

(Source:Holland Innovation Team)

 

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Fuel cell technology is emerging as a base-load power generation technology as well as back-up power for intermittent renewable energy such as solar and wind, substituting conventional storage batteries. However, Fuelcell requires a Fuel in the form of Hydrogen of high purity. The advantage of Fuel cell is, its high electrical efficiency compared to conventional fossil fuel power generation technology, using Carnot cycle. Fuel cell is an electro-chemical device like a battery and generates power using electro-chemical redox reaction silently with no gaseous emission, unlike engines and turbines with combustion, rotary movements and gaseous emissions. The fuel Hydrogen can be generated using a renewable energy sources such as solar and wind as described in my previous articles, “Solar Hydrogen for cleaner future” dated 4 July 2012, and “Renewable Hydrogen for remote power supply “dated 28 June 2012.

Alternatively, Hydrogen can also be generated using biomass through Biogas. Biogas is an important source of renewable energy in the carbon constrained economy of today’s world. The biogas can be generated from waste water and agro-waste by anaerobic digestion using enzymes. Biomass such as wood waste can also be gasified to get syngas, a mixture of Hydrogen and Carbon dioxide. In anaerobic digestion, the main product will be methane gas accompanied by carbon dioxide and nitrogen while the main product in gasification will be Hydrogen, carbon monoxide and carbon dioxide and oxides of Nitrogen. Whatever may be the composition of the resulting gas mixture, our focus will be to separate methane or Hydrogen from the above mixture. In anaerobic digestion, the resulting Methane gas has to be steam reformed to get Hydrogen gas suitable for Fuel cell application. In gasification, the resulting Syngas has to be separated into pure Hydrogen and Carbon dioxide so that pure Hydrogen can be used as a fuel in Fuel cell applications. As I have outlined in many of my previous articles, Hydrogen was the only fuel we have used all these years and we are still using it  in the form of Hydrocarbons and it will continue to be the fuel in the future also. The only difference is future Hydrogen will be free from carbon.

We have to discuss two issues to mitigate Carbon emission, and it can be done by 1.Elimination of Carbon from the fuel source. 2. Generation of Renewable and Carbon free clean energy directly from solar and wind. One option  to cut Carbon from the fuel source is to use Biomass as the raw material to generate Hydrogen so that fresh Carbon will not be added  into the atmosphere by emissions .The second option is to generate pure Hydrogen from water by electrolysis using renewable energy such as wind and solar. Environmentally friendly waste-to-energy projects are becoming popular all over the world. But now most of these waste-to-energy projects generate either Biogas (Methane) by anaerobic digestion or Syngas (Hydrogen and Carbon dioxide) by gasification. Both these gases need further purification before they can be used as a fuel for power generation. The Methane content in the Biogas (about 60% methane and 40% Carbon dioxide with other impurities) needs to be enriched to 90% Methane and free from other impurities. The composition of a typical Biogas is shown in table1.

The resulting purified methane gas will be reformed using steam reformation in presence of a catalyst to get syngas; finally Hydrogen should be separated from resulting syngas so that it can be used directly into the Fuelcell.The common Fuel cell used for this application is invariably Phosphoric acid fuel cell.

PAFC uses 100% Phosphoric acid in Silicon carbide matrix as an electrolyte. PAFC is a self-contained unit completely enclosed in a cabin consisting of a gas reformer, Fuellcell power generator, Power conditioning unit and other auxiliaries. The PAFC is of modular construction with capacities ranging from 100Kw up to 500Kw as a single unit. It can be installed outdoor in the open and it can be readily connected to a piped Biogas. It can also be connected to existing piped natural gas or LPG bullet as a stand-by fuel. Any waste-to energy project can be integrated with Fuel cell power generation with CHP application to get greatest economic and environmental benefits. Hydrogen derived from biomass will be an important source of fuel in the future of clean energy; and Fuel cell will become an alternative power generation technology for both stationary power generation and transportation such as Fuel cell car or Hybrid cars.

PAFC is a compact, self-contained power generation unit that is used even for base load power. The electrical efficiency of PAFC  is about 42% .It is suitable for CHP applications so that the total energy efficiency can reach up to 85%.It is ideal for supplying continuous power 24×7 and also to use waste heat for space heating or space air-conditioning with an absorption chiller in CHP applications. The ideal candidates for PAFC power generation using CHP will be hospitals, super markets, Data centers, Universities or any continuous process industry.PAFC is now used as a backup power for large-scale renewable energy project with an access to piped natural gas. A schematic flow diagram of a fuel cell power generation is shown in Fig 3 using biogas at Yamagata sewage treatment plant in Japan. Biomass  based  Fuecell  power generation has a great potential all over the world irrespective of location and size of the country.

Nature has a wonderful way of capturing Carbon and recycling it through a process called ‘carbon cycle’ for millions of years. The greenhouse gases in the atmosphere were restricted  within certain limits when it was left to Nature. But when human being started burning fossil fuels to generate power or to run cars, the GHG emission surpassed the limit beyond a point where global warming became an issue. The GHG level has increased to 392 ppm level for the first in our long history. Many Governments and companies are exploring various ways and means to reduce greenhouse emissions to avoid global warming. Some Governments are imposing taxes on carbon emission in order to reduce or discourage such emissions. Others are offering incentives to promote alternative energy sources such as wind and solar. Some companies are trying to capture Carbon emission for sequestration.

While we try to capture Carbon and store them underground, there are many potential commercial opportunities to recycle them. This means the Carbon emission is captured and converted into a commercial fuel such as Gasoline or Diesel or Methane so that future sources of fossil fuels are not burnt anymore. But this is possible only by using ‘Renewable Hydrogen’. Hydrogen is the key  to reduce carbon emission by binding carbon molecules with Hydrogen molecule, similar to what Nature does.

When NASA plans to send a man to Mars they have to overcome certain basic issues. Mars has an atmosphere with 95% Carbon dioxide, 3% Nitrogen, 1.6% Argon and traces of oxygen, water and methane.Nasa is planning to use Carbon dioxide to generate Methane gas to be used as a fuel and also generate water by using the following reaction.

CO2 + 4H2—–CH4 + 2 H2O

2H2O——-2H2 + O2

The water is electrolyzed to split water into Hydrogen and Oxygen using solar power. The resulting Hydrogen is reacted with Carbon dioxide from Mars to generate Methane gas and water using a solid catalyst. This methanation reaction is exothermic and self sustaining. How this can be achieved practically in Mars in those conditions are not discussed here. But this is a classical example on how the Carbon emission can be tackled to our advantages, without increasing the emissions into the atmosphere. There are several methods available to convert Carbon emission in to valuable products including gasoline. The  reaction of the methane with water vapor will result in Methanol.

2H2 + CO——– CH3OH

On Dehydration, 2CH3OH —– CH3COCH3 + H2O.Further dehydration with ZSM-5 Catalyst gives Gasoline 80% C5+ Hydrocarbon. Gas to liquid by Fischer-tropic reaction is a known process.

Carbon dioxide is also a potential refrigerant to substitute CFC refrigerants that causes Ozone depletion. Carbon recycling is a temporary solution to mitigate Greenhouse gas emission till Hydrogen becomes an affordable fuel of the future. It depends upon individual Governments and their policies to make Hydrogen affordable. Technologies are available and only a political will and leadership can make Hydrogen a reality.

It is clear substituting fossil fuels with Hydrogen is not only efficient but also sustainable in the long run. While efforts are on to produce Hydrogen at a cost in par with Gasoline or less using various methods, sustainability is equally important. We have necessary technology to convert piped natural gas to Hydrogen to generate electricity on site to power our homes and fuel our cars using Fuelcell.But this will not be a sustainable solution because we can no longer depend on piped natural gas because its availability is limited; and it is also a potent greenhouse gas. The biogas or land fill gas has the same composition as that of a natural gas except the Methane content is lower than piped natural gas. The natural gas is produced by Nature and comes out along with number of impurities such as Carbon dioxide, moisture and Hydrogen sulfide etc.The impure natural gas is cleaned and purified to increase the Methane content up to 90%, before it is compressed and supplied to the customers. The gas is further purified so that it can be liquefied into LNF (liquefied natural gas) to be transported to long distances or exported to overseas.

When the natural gas is liquefied, the volume of gas is reduced about 600 times to its original volume, so that the energy density is increased substantially, to cut the cost of transportation. The LNG can be readily vaporized and used at any remote location, where there is no natural gas pipelines are in existence or in operation. Similarly Hydrogen too can be liquefied into liquid Hydrogen. Our current focus is to cut the cost of Hydrogen to the level of Gasoline or even less. Biogas and bio-organic materials are potential sources of Hydrogen and also they are sustianable.Our current production of wastes from industries business and domestic have increased substantially creating sustainability isues.These wastes are also major sources of greenhouse gases and also sources of many airborne diseses.They also cause depletion of valuable resources without a credible recycling mechanisms. For example, number of valuable materials including Gold, silver, platinum, Lead, Cadmium, Mercury and Lithium are thrown into municipal solid waste (MSW) and sewage. Major domestic wastes include food, paper, plastics and wood materials. Industrial wastes include many toxic chemicals including Mercury, Arsenic, tanning chemicals, photographic chemicals, toxic solvents and gases. The domestic and industrial effluents contain valuable materials such as potassium, Phosphorous and Nitrates. We get these valuable resources from Nature, convert them into useful products and then throw them away as a waste. These valuable materials remain as elements without any change irrespective of type of usages.Recyling waste materials and treatment of waste water and effluent is a very big business. Waste to wealth is a hot topic.

The waste materials both organic and inorganic are too valuable to be wasted for two simple reasons. First of all it pollutes our land, water and air; secondly we need fresh resources and these resources are limited while our needs are expanding exponentially. It is not an option but an absolute necessity to recycle them to support sustainability. For example, most of the countries do not have Phosphorous, a vital ingredient for plant growth and food production. Bulk of the Phosphorus and Nitrates are not recovered from municipal waste water and sewage plants. We simply discharge them into sea at far away distance while the public is in dark and EPA shows a blind eye to such activities. Toxic Methane gases are leaking from many land fill sites and some of these sites were even sold to gullible customers as potential housing sites. Many new residents in these locations find later that their houses have been built on abandoned landfill sites. They knew only when the tap water becomes highly inflammable when lighting with a match stick. The levels of Methane were above the threshold limit and these houses were not fit for living. We have to treat wastes because we can recover valuable nutrients and also generate energy without using fresh fossil fuels. It is a win situation for everybody involved in the business of ‘waste to wealth’.

These wastes have a potential to guarantee cheap and sustainable Hydrogen for the future. Biogas is a known technology that is generated from various municipal solid wastes and effluents. But current methods of biogas generation are not efficient and further cleaning and purifications are necessary. The low-grade methane 40-55% is not suitable for many industrial applications except for domestic heating. The biogas generated by anaerobic digestion has to be scrubbed free of Carbon dioxide and Hydrogen sulfide to get more than 90% Methane gas so that it can be used for power generation and even for steam reforming to Hydrogen generation. Fuel cell used for on site power generation and Fuel cell cars need high purity Hydrogen. Such Hydrogen is not possible without cleaning and purifying ‘ biogas’ much. Hydrogen generation from Biogas or from Bioethanol is a potential source of Hydrogen in the future.

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