**3. Discussion**

Today, we are in an "oil economy," as crude oil is the basis for a major share of energy and materials production. With an accelerating shift toward a circular economy and renewable resources, a paradigm change is about to happen. Biorefineries and biobased products are seeing strong interest from various stakeholders, as do renewable energies, such as wind and solar.

However, when a realistic view is applied, one will quickly see that decarbonization is not that simple. Biomass and hydrogen will play an important role, for sure; the major issue with stepping out of oil is the sheer size of the industry. When one wants to replace the feedstock for 400 million tons of polymers per year, and for hundreds of millions of tons of base chemicals, agricultural resources are simply not sufficiently available, at least not without creating serious disruptions in feed and food production. There is not only a distribution problem of feed and food but a more fundamental land scarcity issue. We are simply not able to convert all "unmanaged" land into fields and pastures to cater to the world population not only for food but also for materials. Neither can be the productivity of the existing land be pushed upwards indefinitely; for fast, secure, and reliable scale-up of SCP, biopolymer, and other materials produced from non-agricultural and nonoil sources, methane from natural gas seems to be the one option.

Based on the circular economy concept, deriving nutrients from (bio)waste is a sustainable approach. For an analysis of SCP made from biowaste as a feed additive using, see Refs. [164, 165].

#### **3.1 SCP**

In **Table 27**, the market of alternative protein sources is summarized.

As **Table 27** exemplifies, the "farm gate" price of vegetable protein is rather low. Production volumes of alternative protein from microbes are tabulated (**Table 28**).

Today, yeast is undoubtedly the largest volume SCP source, also for food applications.

In Ref. [167], SCP production by the yeast *Kluyveromyces marxianus var marxianus* is described.


#### **Table 27.**

*Different animal and vegetable protein sources compared by their production volumes and prices.*


#### **Table 28.**

*Current status of different microbial proteins based on their market size and production volumes.*

The FeedKind™ plant is currently under construction [168], Profloc™ went out of business.

When we assume a protein demand per person of 70 g per day of SCP, with a world population of 7.9 billion people, the theoretical market potential for bacterial SCP would be 0.5 million tons per day or 200 million tons per year. At a conversion ratio of 1 g CH4 to 1 g of SCP, we arrive at 288 million m<sup>3</sup> of methane, which is approximately 7% of today's natural gas consumption. So if we were to provide all protein for humanity by bacterial SCP, only a fraction of the natural gas stream would be required.

Bacterial single-cell protein has also been envisioned as a possible protein source in a global food catastrophe, where agricultural protein production is suddenly impaired, as elaborated by Juan B. Garcia Martinez [169, 170].

#### **3.2 Bioplastics**

Today, bioplastics have a market share of 1–2% of conventional plastics materials. It is estimated that bioplastics could replace 90% of petrochemical plastics, particularly in standard application like packaging (only for high-performance materials, such as PEEK or PFTE, no suitable bioplastics counterparts is yet known to exist). **Table 29** takes a look at which bioplastics could replace the most common petrochemical plastics. For instance, LDPE could be replaced to some extent by a "drop in" material of similar property set (bio-PE), and by biopolymers with different characteristics, such as PBAT, PBS, and PHA, to the other part.

As **Table 29** shows, a handful of "drop-in" and degradable bioplastics can replace the most common petrochemical plastics. Overall, it is estimated that up to 90% of conventional polymers can be replaced by biopolymers. The benefits of such a replacement are depicted in **Figure 5**.

For simplification, the land use of petroplastics is set to zero, as it is negligible. Also, as **Figure 7** shows, the water use of petroplastics is low. The error bars indicate


*Value-Added Products from Natural Gas Using Fermentation Processes: Products… DOI: http://dx.doi.org/10.5772/intechopen.104643*

#### **Table 29.**

*Overview of the technical substitution potential of regular plastics (left columns) by bioplastics.*

**Figure 5.**

*GWP (global warming potential), land use, and water use of petrochemical and bioplastics packaging materials. Source: [86].*

the possible range of the figures. According to IfBB [171], the footprint of bioplastics is considerable. For instance, 1 ton of PHB requires 2.86 tons of sugar (glucose) or 3.24 tons of starch for its production. One ton of PLA requires 1.47 tons of sugar or 1.67 tons of starch. Yields of crops differ, for example, 10.03 tons of sugar/ha for sugar beet and 0.83 tons of starch/ha for wheat, resulting in specific land requirements for the materials' feedstocks, see **Figure 6**.

**Figure 6.**

*The footprint of the two bioplastics PHB and PLA. Source: [171].*

PLA today is the most important bioplastics material, and there is a shortage of supply in the market, leading to a surge in prices. The strong growth is expected to continue. Major producers of PLA are Total/Corbion (Purac™) and Cargill/ Natureworks (Ingeo™). The PHB market cannot be considered mature, as the volume is still minute, but there are several established players, see **Table 30**.

Taking an existing biopolymer and devising a more cost-effective production technology is more likely to bring success than trying to synthesize and/or isolate a totally novel bioplastics material. Hence PLA and PHB are promising materials for methanotrophic fermentation.

Taking 90% of 400 million tons of polymers and a conversion ratio of 1 g of polymer per g of methane, we see that roughly 13% of the global natural gas production would be required to provide the feedstock for the plastics. When we further assume that in the future, a significant share of polymer materials will be recycled, the demand for virgin polymers will be lower, also reducing the fraction of natural gas needed to cater to it.


**Table 30.** *Players in the PHB market today (status 2016).* *Value-Added Products from Natural Gas Using Fermentation Processes: Products… DOI: http://dx.doi.org/10.5772/intechopen.104643*

Scale-up of PHB production by methanotrophic fermentation is discussed in Refs. [172–175].
