**1. Introduction**

While most petrochemicals are made from crude oil, they are also accessible through natural gas or coal. For instance, synthesis gas can be converted to various hydrocarbons through Fischer Tropsch synthesis [1], which was performed on a large scale in economies without access to oil in times of war (Germany) or Apartheid (South Africa). Over the last 50 years, petrochemicals have seen stronger growth than other materials such as steel or aluminum, because of cheap crude oil and the versatility of the products. It was particularly the plastics that have experienced a tremendous increase in use. The importance of oil and gas for various industries is depicted in **Figure 1**.

As one can see from **Figure 1**, approx. 14% of crude oil (left) and 8% of natural gas (right) are deployed to produce petrochemicals. These are first some standard "base chemicals" or building blocks, from which a huge variety of materials can be derived at low-cost in large quantities.

From natural gas, today chiefly hydrogen, methanol and ammonia are made. Ammonia is used for urea and fertilizer production, for instance. The importance of natural gas as feedstock [3] varies with geography and is shown in **Figure 2**.

The key question, in times of an impending huge energy transition towards renewables, is which trajectory petrochemicals will take in the two or three decades to come, whether crude oil will continue to dominate or whether, e.g., coal or natural gas will be brought in as main feedstocks, or possibly even biomass, in the medium turn. In the long run, i.e., 2050 and beyond, it can be assumed that biomass will have become the dominant feedstock.

**Figure 1.**

*How crude oil (left) and natural gas (right) are used. Source: [2].*

#### **Figure 2.**

*Feedstocks and primary products. COG = coke oven gas; HVC = high value chemicals; Mtoe = million tons of oil equivalent. Source: [2].*

*Value-Added Products from Natural Gas Using Fermentation Processes: Fermentation of Natural… DOI: http://dx.doi.org/10.5772/intechopen.103813*

**Figure 3.**

*Source: CO2 emissions and energy demand for materials in 2017. The final energy demand is given in Mtoe (million tons of oil equivalent). Source: [2].*

The world population is growing [4], and industrialization and economic development are moving ahead. Hence, the demand for petrochemicals is bound to further increase. For plastics (thermoplastics), it can be expected that the historic growth rate of ~6%/year will go down significantly, and that more recycling will be implemented. Other products, such as fertilizers, cannot be turned into a circular economy concept as easily as for instance polymers, so with them, demand most probably will continue to rise.

The energy consumption and its source in different industries is another important aspect. Let us take a look at **Figure 3**, the energy demand and the CO2 emissions (footprint) of 5 vital sectors.

Iron and steel, as well as cement, today are very carbon-intense industries, due to the processes which are being used. Global cement production consumes on the order of 6% of global primary energy demand, mainly by combustion of fossil fuels in the rotary kiln reactors and due to the large production volumes on the order of

#### **Figure 4.**

*Part of a Sankey diagram in the chemical sector: Approx. 200 million tons/year of natural gas and NGL (natural gas liquids) are converted into NH3 (which is then processed to fertilizer) and other products. Source: [6].*

4.1 billion tons/year [5]. Iron and steel still rely to a large extent of the blast furnace, being fuelled by coke, but less carbon-emitting reducing agents are being tested and implemented, such as CH4 or H2, as well as more electric arc furnaces particularly for the increasing share of recycled steel (scrap smelting). Chemicals account for significant energy demand, too, from various processes. **Figure 4** looks at the mass flow in the chemical sector.

As **Figure 4** shows, coal plays a minor role today, and crude oil dominates. Natural gas has a significant share, though. Decarbonization by moving to a less carbon-intense feedstock such as CH4 will be a key driver in the industry in the decades to come. Natural gas is less carbon-intense than crude oil and coal, so one might see more natural gas conversion to chemicals.

## **1.1 Natural gas today**

Natural gas is an established fossil fuel, with existing infrastructure in many parts of the world. It is considered as a "clean" fuel, which burns without ash or significant soot production, and releases less CO2 per unit of energy delivered than do oilderived fuels or particularly coal-based heating materials. The main constituent of natural gas, methane (CH4), can also be sourced and be distributed through the grid from alternative sources such as landfills ("landfill gas") or anaerobic digestion facilities ("biogas"). There is also a strong link towards renewables, though the option of storing (excess) wind energy or (excess) photovoltaic energy in the huge natural gas network under the P2G (power2gas) [7] concept, as hydrogen or as methane (which can be made from H2 in the Sabatier process). The market size of natural gas is on the order of 1000 billion USD per year, and it amounts to approx. 4000 billion m3 /year [8]. 24% of the global energy mix comes from natural gas, which is double the contribution from renewables today. For electricity, the share of natural gas is even higher, where it lies at 55.7% (and at 38.1% for renewables, for comparison). Almost all countries rely on natural gas to some extent. It is the UAE, Russia, Iran, Qatar, Oman and Algeria that are gas-based economies [9]. Methane emissions from industrial operations (production, distribution and use) have lately been identified as a significant and previously underestimated contribution to climate change, and can be addressed by organizational and technological means, see later.

Pipeline transport offers the lowest unit cost for short distances for natural gas. Other methods exist, too, e.g., LNG (liquefied natural gas) [10], particularly for economic long-haul transportation.

#### **1.2 Projection on natural gas utilization**

The IEA World Energy Outlook [9] is an authoritative reference work, updated annually to provide trustful projections of global energy developments. According to the latest 2021 report by IEA (WEO-2021), the natural gas demand is believed to increase over the next 5 years, which is the case for all scenarios considered. After that period, one can see sharp divergences in the different scenarios. The report states that *"Today, natural gas is the largest source of electricity in advanced economies and its level of use remains broadly stable in those economies over the next decade, while it increases by about one-third in the emerging market and developing economies, helping to moderate the use of coal"*, according to IEA [9]. **Figure 5** shows the scenarios.

For their latest report WEO-2021, IEA has modeled four scenarios:


*Value-Added Products from Natural Gas Using Fermentation Processes: Fermentation of Natural… DOI: http://dx.doi.org/10.5772/intechopen.103813*

**Figure 5.**

*Demand for oil, natural gas and coal according to IEA, in the STEPS (stated policies scenario) in the reports of 2016 (blue), 2020 (green) and 2021 (red). One can see that the new report is much less in favor of fossil fuels than previous projections. Source: [9].*


*"The NZE is normative, in that it is designed to achieve specific outcomes – an emissions trajectory consistent with limiting the global temperature rise to 1.5 °C without a temperature overshoot (with a 50% probability), universal access to modern energy services and major improvements in air quality – and shows a pathway to reach it. APS and STEPS are exploratory, in that they define a set of starting conditions, such as policies and targets, and then see where they lead based on model representations of energy systems, including market dynamics and technological progress. The SDS is also normative, mapping out a pathway consistent with the "well below 2 °C" goal of the Paris Agreement, while achieving universal access and improving air quality"* [11].

The historic price development of the fossil fuels natural gas, coal and oil is depicted in **Figure 6** [9].

**Figure 6.** *Regional oil, coal and natural gas prices from 2010 to 2021. MBtu = million British thermal units. Source: [9].*

One can infer from **Figure 6** that natural gas is less volatile than oil, and can be on the lowest unit costs level.

In the STEPS scenario, the demand for natural gas will increase to approx. 4500 billion m3 by 2030 (which is 15% higher than in 2020) and to 5100 billion m3 in 2050. According to IEA, there will be a rise in natural gas utilization both in industry and in the power sector, and it will remain the standard for space heating.

By contrast, the APS scenario predicts a peak of natural gas use shortly after 2025, followed by a decrease to 3850 billion m3 by 2050. *"Countries with net zero pledges move away from the use of gas in buildings, and see a near 25% decrease in consumption in the power sector to 2030".*

In the NZE scenario, the demand for natural gas is forecast to drop even more sharply from 2025 onwards and will fall to 1750 billion m3 in 2050. *"By 2050, more than 50% of natural gas consumed is used to produce low-carbon hydrogen, and 70% of gas use is in facilities equipped with CCUS".* (CCUS = carbon capture, utilisation and storage). Likewise, we can expect more natural gas being deployed for the production of additional materials.

**Figure 7** offers a visual depiction of the scenario projections.

An interesting aspect worth noting from **Figure 7** is that biogas is forecast to have a relevant role in all scenarios, on the order of 5% of natural gas volumes, being at ~double the level of 2020 production. It is complemented by hydrogen to various degrees. Natural gas demand changes per scenario are detailed in **Figure 8**.

Only emerging markets and developing economies are expected to use more natural gas, as do industry and hydrogen production. Details on the projected natural gas consumption per region are shown in **Figure 9**.

One can observe from **Figure 9** that in all 3 scenarios, up to 2050, natural gas use in Europe will decline.

**Table 1** shows the remaining natural gas resources in terms of "technically recoverable natural gas".

As **Table 1** demonstrates, it is in the Middle East and Eurasia where most of the proven reserves of natural gas are sitting. All regions have significant proven reserves and even more resources, so that availability is not the determining factor for natural gas use but rather other factors such as climate change considerations.

**Figure 7.**

*Left: Timeline of natural gas use; right: Supply of low emissions gasses in 2030. Bcm = billion m3 . Note: Hydrogen gases are inclusive of low-carbon gaseous hydrogen and synthetic methane with 1 EJ = 29 bcm. Source: [9].*

*Value-Added Products from Natural Gas Using Fermentation Processes: Fermentation of Natural… DOI: http://dx.doi.org/10.5772/intechopen.103813*

#### **Figure 8.**

*Development of natural gas demand from 2020 to 2030. Bcm = billion m3 . Source: [9].*

#### **Figure 9.**

*How natural gas production is expected to change by region and scenario from 2020 to 2050. Bcm = billion m3 ; C & S America = central and South America. Source: [9].*


#### **Table 1.**

*The remaining "technically recoverable" resources of natural gas. Source: [9].*
