Renewable Gas : Scenes From The Very Near Future : 2

The Forest is an Energy Field

Location : Scottish Highlands
Year : About 20 years from now
Time of Year : Autumn
Time of Day : Morning
Temperature : 14 degrees C
Weather Conditions : Slightly dewy; clean, cold air; weak sunlight; with a slight breeze.

A team of three forest reclamation engineers begin their morning rounds in an open-top electric vehicle.

The company transporter travels on the reclaimed glass and polymer track so quietly through the mixed plantation that it does not even disturb a convention of jet black crows cawing in the copper-carpeted inspection clearing.

As the biomass harvesting assessors step off the porous crystal roadway, the crows are momentarily startled by boots crunching the crisp leaves given up by the trees and dried by the sun.

A little residual mist hangs about in the nearest gathering of trees, busy maintaining their microclimate, despite the unseasonably dry weather. The chill of the early hours is wearing off, as the sun weakly begins to warm the tree canopy.

This is giant, managed mixed forest of species that include native British trees for this region, and include the traditional pine and conifer. With the changing average temperatures and rainfall, gradual experimentation is taking place to discover the ideal mix of trees that will offer both fast growth, good canopy cover and good processing quality.

These trees are destined for the furnace, but not ordinary combustion. They will be gasified at high temperatures in the presence of a specialised mix of salts, metal grains and ground rock powder, to capture the maximum energy value of the hydrogen and the carbon in all kinds of wood, including forest thinnings and mill chippings, and pipe this synthetic gas to an industrial gas processing plant.

The aim for the day is to do an accounting exercise to answer the question of whether this settlement is ready for harvest. A nearby dense copse is selected for analysis. The trees will not be extracted unless the potential for carbon sequestration and carbon recycling is highest according to the study.

The old practice in forestry clearance was to log – saw the trunk of each tree, strip the branches and as much bark as possible – and drag the poles away. Logging in this way has been outlawed. Significant branch, bark and leaf litter from harvesting trees is no longer permitted, as this can lead to high methane emissions. In addition, the soil at tree extraction sites must be immediately protected from erosion, desiccation and outgassing, as the earth is an important part of the overall forest carbon sink.

What needs to happen now is that for every tree that is removed, a young stripling is planted in a very nearby location. This will allow the young tree to benefit from the dying root system of the extracted tree. In addition, as much of the tree as possible is removed, as all the biomass can be used for energy, chemicals and materials purposes.

A key part of the restoration strategy after harvesting high trees is also growing forest crops, to make use of the extra available sunlight as the leaf canopy has been removed. The cropping plants need to be tended, pollarded or picked regularly – depending on whether the crops are for biomass or food – and then finally removed, when the young replacement trees become large enough to form a dense canopy of their own.

The team of forest surveyors are looking for treefall and other unusual quantities of forest floor litter, because they have grown accustomed to previously unknown diseases and infestations breaking out in these plantations. It is important that outbreaks are swiftly cleared, or vast tracts of wood can be lost, as was the case in early twenty-first century native Canadian boreal zones.

This forest is designed to be easily harvested : there are wide lanes between large copses or stands, wide enough to contain and constrain both wildfire and diseases : large area wildfire previously unprecedented in this part of the world. There are artificial as well as natural burns, tarns and canals at regular intervals, which help with material transportation as well as provide relief from singeing when there is a local fire.

Every plantation has its own gas-making plant, as this reduces energy lost to transporting woods. Turning tree into gas permits the capture of the carbon from more of the tree, preventing forest litter decomposing and releasing methane to the sky. It also sustains the energy industry, as gas can be stored to provide electricity generation when the weather is dark and calm.

Despite the massive rollout of wind power and solar power, there are still weeks of low renewable electricity generation from these sources, so backup in the form of gas is still necessary; however, nobody is permitted to mine for Natural Gas any longer.

The vast caverns of Natural Gas that were discovered and exploited in the 20th century petered and puffed out, or were found to be too contaminated to mine; and the only thing being pumped was carbon dioxide, hydrogen sulfide and nitrogen from the North Sea. Plus, the voiding caverns started to cause earthquakes, which disrupted the energy industry infrastructure and shipping lanes.

The fossil fuel offshore industry was gradually being replaced by the wind power industry anyway, so it was a natural progression to close down the Natural Gas mining. The oil with the Natural Gas was becoming more and more degraded : the quality was reducing sharply as more and more gas was being used to inject to keep up the oil flow pressure in the reservoirs. And the good quality oil was long gone. The remaining raw crude petroleum oil was contaminated by sulfur and brine, and the energy wasted in refining it made it uneconomic to extract in the middle of the 21st century.

The North Sea oil and gas industry gradually evolved : first came offshore wind power : great windmills fixed to the seabed or floating on giant pontoons. Then, came green hydrogen, as the giant wind turbines produced so much power, it could not all be used at the time it was generated. The former oil companies had already become gas majors, so it was a logical step for them to become green gas producers, retaining the same economic place and industrial role they had already. It kept pensions and government tax revenue streams safe.

Some of the formerly fossil fuel internationals turned to solar sea power, but they could not make it work economically because of changes in the gyres and storms, making previously quite calm areas too choppy to float solar arrays. However, they did branch out into solar farming on land, in the degraded farmlands near their formerly oil terminals and petrorefineries.

To maximise gas production, green methane from gasification of biomass was added to the resources of green hydrogen produced from renewable power : it permitted a wider variety of resources to be utilised for gas, and also provided carbon-based molecules for the burgeoning green chemistry industry.

Almost anything with carbon and hydrogen in it can be gasified, including almost every part of a tree. Water is often used somewhere in the process, so a place with forests and river systems, lakes or lochs are ideal. The products will be the four main gases : methane, hydrogen, carbon monoxide and carbon dioxide.

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