water engineering

Overall summary

The major problems facing the agricultural area across the globe are greenhouse gas emissions, soil contamination, and the use of nonrenewable energy. According to the existing literature, biochars and hydrochars can play a huge role in addressing these problems. Over the past few years, there is a significant increase in the need to utilize biomass which is often obtained from char products in different fields. This can be attributed to the efforts geared towards addressing some of the common challenges affecting the environment and energy sectors across the globe. such challenges include the CO2 emissions, energy catastrophe, and pollution of the environment. As a result of this, a number of scholars have weighed in on the production of biochar and hydrochar. The existing literature review provides a good insight into the production, classification and ultimate utilization of biochar and hydrochar. In addition to this, some papers offer important information regarding the basic principles of production and appliances required for the reactions in the formation of biochar and hydrochar. Zhang et al. (2019) analyze the balance between energy and the economic rigidity of the technology used in the production of biochar. Also, the authors provide a comparison between the impact of altering the temperature of reaction, use of different types of feedstock, and the modes of thermochemical conversion on biochar.

The existing literature on biochar and hydrochar offers highlights of the advantages and possible hindrances associated with promoting the application of biochar and hydrochar in the environmental and energy sectors (Park, Lee, and Kim 2018; Taskin et al. 2019; Li et al 2018; Kambo and Dutta 2015). Such applications include, but not limited to, adsorbents, building blocks for catalysts, modification of soil, anaerobic breakdown and formation of manure, and storage materials for electrochemical energy. This literature review, therefore, provides a summary of the recent technological developments in relation to engineered biochar and hydrochar. Additionally, this literature review is a piece of evidence showing the direction in which biochar and hydrochar research is headed as well as the expected developments in this regard.

The key viewpoints from the existing literature can be summarized in the itemized findings hereunder. These viewpoints are listed with the sequence of their importance level.

1. Biochars and hydrochars can be used to a great effect in the modification of soils. This can be attributed to the varying ability of biochars and hydrochars to retain nutrients as well as toxic elements. Taskin et al. (2019) provide a useful guideline for determining the most appropriate biochar or hydrochar to be used in a specific type of soil. According to them, the feedstock and mode of production of biochars and hydrochars often affect the attributes of the resulting chars. On the other hand, Fornes et al. (2017) noted that biochars and hydrochars can also be used to modify soils, particularly to achieve the desired ability for soils regardless of their size of particles.

2. There is an increase in the use of renewable energy over the past few years. Due to the increased technological advancements in the energy sector, it is possible to utilize waste materials to generate energy. Park, Lee, and Kim (2018) discuss how algal biomass can be used to produce hydrochars which are utilized in the production of solid energy through hydrothermal carbonization. On their part, in relation to the production of energy, Xiao et al. (2018) sought to determine the correlation between complex chemical structures of an orange peel as a bio-waste and the physicochemical constitution of an orange peel derived hydrochar.

3. Hydrochars and biochars are utilized in addressing the global phenomenon of greenhouse gas emissions. According to Li et al. (2018), the greenhouse gas emission from the soil is significantly reduced by adding biochars and hydrochars which alter the chemical composition and PH attributes of the soil. Gases such as methane, CO2, and N2 are therefore absorbed into the soil but not released as the hydrochars and biochars help the soil to retain them. In their study, Kambo and Dutta (2015) offer an invaluable review of the production and application of biochars and hydrochars that forms a basis for determining the most appropriate chars to be used in controlling greenhouse gas emissions.

Based on the literature review below, it is evident that biochars and hydrochars to be utilized in promoting food security in developing countries. The data obtained in the literature reviewed above can be used to confirm that hydrochars can be used to grow crops in arid areas provided conditions such as irrigation are put in place. Simple research can, therefore, be carried out to determine whether biochars and hydrochars can be used to retain nutrients and moisture in such areas for long to facilitate the growth of crops. Information gathered from the study by Kambo and Dutta (2015) is useful.

Literature Review

The article by Fornes et al. (2017) can be categorized as an application investigation. It reveals how biochar and hydrochar can be utilized in the production of containerized tomatoes. The paper gives detailed steps to be used when using hydrochar and biochar in containerized tomato production. The objective of this paper is to determine the effects of chars on soils and ultimately on the production of containerized tomato. Fornes et al (2017) set out to discover whether chars affect the growth of plants as well as the quantity of the harvest. Also, the paper is designed to gather information to be used to ascertain whether the quality of the fruits is affected by chars. The use of different types of soils from different regions ensures that the size of soil particles was not the same across the samples of soil collected. Hence, the specific problem under investigation in this paper is nutrient solution retention. The researchers sought to find out how biochars and hydrochars can be utilized to address the issue of low nutrient solution retention. In order to attain the objectives of the study, Forness et al. (2017) prepared three different chars. These included a forest waste biochar, olive mill waste biochar, and a forest waste hydrochar. Besides this, coir was selected in order to provide a common material that is commonly used together with the chars in the production of containerized tomato. The researchers also opted for two varieties of tomatoes which had a significantly different performance. These varieties were the commercial hybrid Gransol RZ and Cuarenteno. A random block design was used to determine the distribution of the tomatoes cultivated in pots across a controlled greenhouse. The innovative aspect of the problem-solving methods was the use of a climatic greenhouse. The researchers chose to equip the greenhouse used in the study with heating and cooling systems. This allowed them to manipulate the temperature of the soils and thus replicate the changes in weather throughout the year. As a result of this, it was possible to obtain data related to the effects of chars on containerized tomato during different seasons of the year. Following this research, there is a need to determine the most suitable feedstock to be used in the production of quality biochar for the production of containerized tomato. In addition to this, there is room for research on the best way to utilize energy obtained from biochar and hydrochar to promote the production of containerized tomato. In my opinion, with regards to addressing the issues facing the area of water resources and environmental engineering the importance level of the problem is high. This is explained by the need to modify soil in order to promote farming activities, particularly growing of food crops. Therefore, the promisingness level of the direction in this paper for future research is highest. There is a need for more similar studies with the focus being on crops other than containerized tomato.

The study by Park, Lee and Kim (2018) can be categorized as a mechanism investigation. The reason for this is that the paper focuses on the char product with the aim of maximizing on the level of carbonization as well as the resulting yield. The paper describes how the reaction temperature can be altered to achieve this. The energy and properties of char products obtained from algal biomass in this study were compared to naturally occurring coal and chars that are got through a thermochemical process. The main problem solved in this paper is reducing the CO2 emissions which are associated with the use of non-renewable energy. This study discusses a way through which the energy produced from algal biomass can be increased. This is possible through hydrothermal carbonization and the resultant energy emits net-zero carbon dioxide emission. The use of algae as a biomass substrate in this paper ensures that the thermal transfer resulting from the temperature is rapid. This can be attributed to the microscopic size of the algae. In this study, the effects of HTC on the properties of fuel and the hydrochars’ dewatering performance were evaluated using a hydrothermal reactor. The experiment was conducted under Nitrogen gas and the components were mixed adequately by use of a 200 rpm rotating agitator. By measuring the capillary suction time, the dewaterability performance of the hydrochars was determined. A PerkinElmer 2400 Series II CHN organic elemental analyzer was utilized to determine the percentage weight of chemical components. The weight percentage of any matter that is volatile, the constant carbon, as well as the ash was established using a TGA-701 thermogravimetric analyzer. Calorimetro AC-350 LECO was also used to establish the calorific values. Under the analytical procedures, the researchers had to improvise a capillary suction time (CST) apparatus. The purpose of the CST apparatus was to evaluate the dewaterability performance of hydrochars after HTC. The improvised apparatus was characterized by a single-radius test and it used the normal CST paper. In my opinion, there is a need to research the most effective ways of promoting the reproduction of algae that will be utilized in the production of solid fuel. Besides this, there is an opportunity relating to this research to make a comparison between the economics related to the value of this form of solid energy and energy produced from natural coal. The information provided in this paper makes the importance level of the problem in the area of water resources and environmental engineering to be highest. The paper promotes the production and use of green energy. However, the promisingness level of the direction in this paper for future research is lowest because the study does not raise new ideas or point out gaps that require further research.

The work by Taskin et al. (2019) is regarded as an application investigation. The reason for this is that the emphasis of the paper lies on the uses of biochar and hydrochar varies as a result of their production parameters and feedstock. The paper provides a multianalytical assessment of chars produced from waste biomass and their subsequent applications. The ultimate problem solved in this paper is the modification of soil using biochar and hydrochar obtained from waste biomasses. The modified soils, in return, are used for various environmental and agricultural applications. Two samples of biochars and two samples of hydrochars were obtained from different regions. The samples of biochar were collected from red sprue wood pellets and grapevine trimming remains. On the other hand, the feedstock for the hydrochar samples obtained comprised of urban trimming residues and an organic portion of solid urban wastes. Both sets of biochar and hydrochar samples were obtained through similar processes of pyrolysis and hydrothermal carbonization respectively. A multianalytical approach was employed in collecting the necessary data to determine the content of mineral and potentially toxic elements found in each of the four samples. Some of the data collected in this study were obtained using the MS Data Review program. This program was used to elaborate the pyrograms and identify compounds based on the GC retention time. The integration of the Wiley/NIST library into the software also facilitated the comparison of the mass spectra. The findings of this study revealed the difference in ability to retain plant nutrients and toxic substances for both hydrochars and biochars. The findings showed potential advantages from the utilization of hydrochar and biochar. However, in my opinion, further research on prevention of environmental pollution brought about as a result of HC and BC should be carried out. Hence, the promisingness level of the direction in this paper for future research is also highest. The importance level of the problem solved in this paper, in my opinion, is high. This is one of the major issues facing the area of water resources and environmental engineering.

Effects of Biochar Application in Forest Ecosystems on Soil Properties and Greenhouse Gas Emissions: A Review by Li et al. (2018) is an application investigation paper. The study focuses on the effects of applying biochar in a forest ecosystem. The paper sets out to reveal how biochars can be utilized to address the issue of greenhouse gas emissions and to improve the quality of soil in order to promote the existence of forests. The quality of forest soil has been impacted negatively as a result of global climate change and the intense management of forest. This has been through decreased organic carbon content in the soil, declining biological properties of the soil, soil acidification, and decreased soil biodiversity. Although, there has been extensive research and documentation on the role of biochar in agricultural soils, less has been done on the effects of biochar in forest soils. This paper focuses on reviewing and summarizing the existing literature on the stated problem. The paper is organized into different chapters with each of them addressing an issue related to the effects of biochar on components of the soil and its impact on greenhouse gas emissions. The authors identified the key areas with regards to the most critical components of soil which affect the existence of forests. This includes, but not limited to, soil nutrients, soil microbial structure, and soil chemical properties. Each of these was presented under subtopics in an orderly and easy to understand manner. In as much as it has been reported that the biochar application on forest soil generally improves the soil quality while extenuating soil greenhouse gas emissions, there is a need for future study particularly on adverse effects of biochar application on forest soil. The authors singled out the work of Dutta et al (2017) which reveals that, in the process of biochar production, there is also production of other materials like polycyclic aromatic hydrocarbons and volatile organic compounds. The author adds that these materials remain on the biochar particles surface. Therefore, tree plant growth and microbial community of soil may be affected negatively by such materials (Dutta et al, 2017). In my opinion the importance level of the problem in the area of water resources and environmental engineering is highest largely because of the wide range of issues discussed in this paper, similarly, the paper offers a high level of promise with regards to future research in the areas of using biochars and hydrochars to contain greenhouse gas emissions.

The paper, Correlations between Hydrochar Properties and Chemical Constitution of Orange Peel Waste during Hydrothermal Carbonization, is a mechanism investigation. The basis of the study revolves around the process of hydrothermal carbonization. The problem solved in this study conducted by Xiao et al. (2018) is handling wastes in the form of orange peels. The main aim of this study was to determine the correlation between complex chemical structures of an orange peel as a bio-waste and the physicochemical constitution of an orange peel derived hydrochar. This orange peel derived hydrochar was intended to be utilized in adjustments of the hydrochar characteristics for particular applications. This was mainly for effective hydrothermal biomass treatment. In order to achieve the stated goal of the study, quantitative research methodology was employed. It was believed that this quantitative research methodology would be more useful as compared to qualitative in this study because correlation is measurable and can be expressed through statistical techniques. In addition to this, there is an existence of quantitative data which was obtained from the orange peel samples. This quantitative data was later analyzed in a linear manner to obtain linear superposition data. For this study, the researchers identified three composition variables of OraPeel material as cellulose, hemicellulose, and lignin. This required them to be innovative enough to extract the three variables from the orange peels obtained from a local market in China. The results indicated the existence of correlation between the chemical structure of the typical bio-waste and hydrochar characteristics. However, further study should be conducted to determine to what extent the orange peel can be used in place of the hydrochar in specific applications. The importance level of the problem solved in this paper is significantly low compared to those in the other articles reviewed herein. The reason for this is that the problem does not directly address any of the major problems facing the area of water resources and environmental engineering. As a result of this, the promisingness level of the direction in this paper for future research is lowest.

The paper written by Kambo and Dutta (2015) is a mechanism investigation as it describes the processes of preparing hydrochars and Biochars. The problem solved in this paper is the identification of an efficient production process for the preparation of biochars and hydrochars. This paper provides a review on the reaction mechanisms and essentials on the slow-pyrolysis and the processes of hydrothermal carbonization. Also, the paper provides the summaries of the physicochemical properties of chars and applications in various industries. Because of reviewing the existing literature to solve the stated paper and provide a summary on the same, the paper employed qualitative research methodology. Unlike quantitative that deals empirical exploration of an observed event via mathematical, computational, or statistical techniques, qualitative explores concepts, meanings, description, and characteristics of things to gather non-numerical data. In the production of hydrothermal carbonization, salt and acids are added in order to improve its physicochemical characteristics and decrease the temperatures and reacting pressure. Additionally, it is believed that the pulverization of hydrochar is less energy exhaustive process in comparing to raw feedstock. Further, the pulverized particles in the process show a spherical shape that accelerates the fluidization procedure in gasification. Liquid water was also used in place of some components like ambient methanol, ambient acetone, ambient hexane, and methylene chloride though under specified temperatures. Though it has been documented that hydrochar (HTC char) is a treasured resource as compared to biochar, it is essential for further research to be conducted on how the HTC char can be utilized effectively in terms of biomass feeding against pressure, its properties and process conditions, the association and effects among feedstock structure and improvements in the hydrochar production. The problem solved in this paper is highly important to the area of water resources and environmental engineering because it unearths efficient ways in which biochars and hydrochars can be produced. By virtue of being a comparative study, there is low promisingness for future research.

References

Fornes, Fernando, Rosa M. Belda, Pascual Fernández de Córdova, and Jaime Cebolla‐Cornejo.

"Assessment of biochar and hydrochar as minor to major constituents of growing media for containerized tomato production." Journal of the Science of Food and Agriculture 97, no. 11 (2017): 3675-3684.

Kambo, Harpreet Singh, and Animesh Dutta. "A comparative review of biochar and hydrochar in terms

of production, physico-chemical properties and applications." Renewable and Sustainable Energy Reviews 45 (2015): 359-378.

Li, Yongfu, Shuaidong Hu, Junhui Chen, Karin Müller, Yongchun Li, Weijun Fu, Ziwen Lin, and Hailong

Wang. "Effects of biochar application in forest ecosystems on soil properties and greenhouse gas: a review." Journal of soils and sediments 18, no. 2 (2018): 546-563.

Park, Ki Young, Kwanyong Lee, and Daegi Kim. "Characterized hydrochar of algal biomass for producing

solid fuel through hydrothermal carbonization." Bioresource technology 258 (2018): 119-124.

Taskin, Eren, Carolina de Castro Bueno, Ignazio Allegretta, Roberto Terzano, Andrè Henrique Rosa, and

Elisabetta Loffredo. "Multianalytical characterization of biochar and hydrochar produced from waste biomasses for environmental and agricultural applications." Chemosphere 233 (2019): 422-430.

Xiao, Kangxin, Huan Liu, Yang Li, Linlin Yi, Xiuju Zhang, Hongyun Hu, and Hong Yao. "Correlations

between hydrochar properties and chemical constitution of orange peel waste during hydrothermal carbonization." Bioresource technology 265 (2018): 432-436.

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