Category Archives: BIOMASS NOW — CULTIVATION AND UTILIZATION

Operation Plan for 24-h Hauling

The plant will operate 24/7, but the Receiving Facility will be open 24 hours per day for 6 days. At 6:00 Sunday morning, there will be enough feedstock accumulated in at-plant storage for the maximum 3-day buffer (72 hours). Hauling operations begin again at 6:00 Monday morning. At-plant inventory is decreased to a 2-day buffer (48 hours) to supply the material for operation from 0600 Sunday morning to 6:00 Monday morning.

To discuss the 24-h-hauling concept, it is convenient to consider SSL operations as: 1) "day — haul" operation, and 2) "night-haul" operations. For the day-haul operation, the racks are transported as they are filled during the day. For the night-haul operation, the required number of empty racks, enough for one day’s operation, are pre-positioned at the SSL. Cost of pre-positioning the racks is not considered in this example. The SSL crew fills these racks with bales during their 10-h workday and they are hauled during the night. Each truck arriving during the night unhooks a trailer with two empty racks and hooks up a trailer with two full racks. The next morning, the SSL crew will fill the empty racks delivered during the night and fill them during their workday.

Study on the safety of water quality by Оз-BAC process

4.1. Safety of microorganism

Because of ecclasis of microorganism and hydraulic erosion, microorganism may release from activated carbon bed, which will cause a series of water quality safety problems. Therefore, the microorganism safety of O3-BAC process is very important for its application.

Microorganism safety of O3-BAC technology should include the following four aspects[63], which characterize microorganism safety from different aspects respectively. Firstly, pathogenic microorganisms and toxic substances produced by their metabolism are the core problems concerning biological safety. Secondly, biocommunity mainly including bacteria, protozoa and metazoan is the expansion of the first aspect, which is based on some kinds of correlativity relationships between the biocommunity and pathogenic microorganisms. Thirdly, there is a certain connection between water quality parameters such as turbidity,
biological particle number and the risk of pathogenic microorganisms. Fourthly, Assimilable Organic Carbon (AOC) is one of the indexes characterizing bacteria regrowth potential. Low AOC indicates a small possibility for bacteria regrowth and low pathogenic microorganisms risk[64].

Correlations exist among those four aspects. Among them, the first and second aspects are relatively intuitive, and have intimate connections with microorganism safety, but not easy to be detected. The third and the fourth aspects are indirect indexes that can be detected quickly and easy to be automatically controlled, which is particularly important to the operation management of water plant.

According to the research and operation practice, O3-BAC process produced abundant biocommunity, but pathogenic microorganisms were not found in the activated carbon and so were significant pathogenic microorganisms in effluent as well[64]. The effluent turbidity maintained under 0.1NTU on the whole, but it may beyond the standard during the preliminary stage (0.5~1h), the later period or the whole procedure of activated carbon bed filtration. Particle number was generally less than 50/ml in outflow, when the system worked stably, thus the microorganism safety can be guaranteed. However, it would reach up to 6000 per milliliter in primary filtration water. On the other hand, the effluent AOC basically maintained under 100 pg/L. According to relevant research result, AOC concentration in 50~100 pg/L could restrain the growth of colibacillus.

On the whole, microorganism safety problems have not been found in O3-BAC process until now, while it must arise enough attention. This problem should be controlled by optimizing design parameters, strengthening the operation management and developing new treatment technology.

Ozonation contact reactor should be set up with more ozone dosing points to guarantee the removal effect of cryptosporidium and giardia insect, and CT value should be greater than 4 generally. The thickness of the activated carbon bed should be greater than or equal to 1.2m in general. In order to guarantee microorganism safety, a sand layer with certain thickness shall be considered to be added under the carbon layer. Besides, setting up reasonable operation period for biological activated bed and strengthening the management of initial filtrated water. If possible, water quality monitoring of every single biological activated carbon processing unit should be taken into account, for example, setting online monitoring equipments for turbidity and grain number. Furthermore, it can be effective by using other processing technologies or combining O3-BAC with other technologies to solve this problem. For instance, reversed O3-BAC and sand filter or O3-BAC and membrane filtration hybrid process (UF and MF) can be applied[65].

Biomass production

Biomass encompasses all plant and plant-derived materials as well as animal matter and animal manure. Due to its abundance biomass has to be considered as a vital source of energy to satisfy the global energy demand. Table 1 shows the breakdown of primary energy sources and their contribution to total world energy demand during 1973 and 2009. It is evident that the contribution from biomass is only 10% over this period and in the global scale bioenergy has not yet made any significant impact. However, according to a report published by the United States Department of Agriculture, biomass derived energy has become the highest contributor among all the renewable sources during 2003. According to US statistics 190 million dry tons of biomass is consumed per year, which is equivalent to

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3% of current energy consumption [5]. Even though it is hard to conceive that biomass can totally eliminate the use of fossil fuel consumption, it can complement the renewable energy sector together with other sources like wind, solar and geothermal energy.

Primary energy sources

1973

2009

The total world energy demand (Mtoe)

6111

12150

Oil

46.00%

32.80%

Natural gas

16.00%

20.90%

Nuclear

0.90%

5.80%

Hydro

1.80%

2.30%

Biofuels and waste

10.60%

10.20%

Coal / peat

24.60%

27.20%

other

0.10%

0.80%

Table 1. The world’s primary energy sources with its contribution. [6]

Production and Renewable Energy

Moses Isabirye, D. V.N Raju, M. Kitutu, V. Yemeline, J. Deckers and J. Poesen

Additional information is available at the end of the chapter http://dx. doi. org/10.5772/56075

1. Introduction

Bio-fuel production is rooting in Uganda amidst problems of malnutrition and looming food insecurity "in [1,2]". The use of food for energy is a Worldwide concern as competition for resources between bio-fuel feedstocks and food crop production is inevitable. This is especially true for the category of primary feedstocks that double as food crops. Controversy surrounds the sustainability of bio-fuels as a source of energy in Uganda.

Given the above circumstances, adequate studies are required to determine the amount of feedstock or energy the agricultural sector can sustainably provide, the adequacy of land resources of Uganda to produce the quantity of biomass needed to meet demands for food, feed, and energy provision. Sugarcane is one of the major bio-fuel feed-stocks grown in Uganda.

Growth in sugarcane cultivation in Uganda is driven by the increased demand for sugar and related by-products. Annual sugar consumption in Uganda is estimated at 9 kg per capita with a predicted per capita annual consumption increase by 1 % over the next 15 years "in [3]".

This growth has resulted in increased demand for land to produce staple foods for households and thus encroaching on fragile ecosystems like wetlands, forests and shallow stoney hills and, a threat to food security " in [4]". The situation is likely to worsen with the advent of technology advancements in the conversion of biomass into various forms of energy like electricity and biofuels. A development that has attracted government and investors into the development of policies "in [5, 6]" that will support the promotion of bio­fuels in Uganda "in [7]".

Competition for land resources and conflicts in land use is imminent with the advent of developments in the use of agricultural crop resources as feedstocks for renewable energy

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production. Sugarcane is one such crop for which production is linked to various issues including the sustainability of households in relation to food availability, income and environmental integrity. The plans for government to diversify on altnertive sources of energy with focus on biofuels and electricity generation has aggravated the situation. This chapter aims at demonstrating how sugarcane biomass can sustainably be produced to support fuel and electrical energy demands while conserving the environment and ensuring increased household income and food security.

This study was conducted with a major objective of assessing sustainable production of bio­fuels and electricity from sugarcane biomass in the frame of household poverty alleviation, food security and environmental integrity.

2. Research methods

The assessment of sugarcane production potential is done for the whole country. The rest of the studies were done at the Sugar estate and the outgrower farmers.

Aboveground biomass

Aboveground biomass pools increased with stand age in both forest management systems as a consequence of steady accumulation (Figure 4). HF follows a typical pattern with high increments in the aggregation phase and marginal accumulation rates after 50 years.

Thinning concentrates additional growth on selected individuals with the highest possible quality, while low quality stems are harvested and utilized as fuelwood or further chipped. Hence the silvicultural activities aim at refining the product instead of maximizing biomass production. Approximately 2/3 of the aboveground biomass corresponds to understorey in the youngest HF site (11 years), while its share decreases steadily with increasing stand age (Table 1). The slightly rising share in the oldest stand (from ~3 to ~5 %) could be explained by initiation of generative regeneration as the canopy opens after thinning operations, allowing seeds to germinate and initiate regeneration.

Site

Age

Biomass stocks [t/ha-1 dry mass]

Biomass stocks [%]

[years]

Overstorey

Understorey

Sum

Overstorey

Understorey

HF1

11

9.8

4.9

14.7

33.3

66.7

HF2

32

81

18.1

99.1

81.7

18.3

HF3

50

111.9

13.9

125.8

88.9

11.1

HF4

74

137.4

4.1

141.5

97.1

2.9

HF5

91

130.3

7.1

137.4

94.8

5.2

CS1

1

133.2

0

133.2

100

0

CS2

15

73.8

31

104.8

70.4

29.6

CS3

26

147.7

36.7

184.4

80.1

19.9

CS4

31

138.7

65

203.7

68.1

31.9

CS5

50

167.5

87.5

255

65.7

34.3

Table 2. Aboveground biomass stocks in tons per ha-1 dry mass for HF and CS, separated into overstorey and understorey compartments. In HF, overstorey represents individuals with DBH > 8 cm, while understorey represents individuals with DBH< 8 cm respectively. In CS, overstorey represents standards and understorey the vegetative coppice regeneration with some individuals being the result of generative regeneration.

In CS, we found a steady increase until the end of the rotation as the stand is still in the aggradation phase. The 15 year old stand is an exception because standards were previously harvested (irregular cut) resulting in lower biomass stocks as compared to the one year old stand where the total biomass equals that of standards. The relationship between overstorey and understorey biomass stocks is typical for coppice with standards forest management. While the overstorey stocks remain relatively constant (between 133 and 168 t. ha-1), except in the 11 year old CS site where standards were recently harvested, the understorey coppice biomass pool constantly increases to 88 t. ha-1 at an age of 50 years (see Table 1). The relative share of coppice biomass increases from 20% in a 26-year-old stand to 34% in the oldest stand. This is an example for adaptive forest management since the demand for fuelwood has been low for decades and we were consequently able to find outgrown CS plots (50 years) and the share of coppice biomass is still relatively low. It could be increased under a different demand structure, where biomass for energetic utilization is in demand and commercialization becomes an interesting option for the forest owner.

image17

stand age (years)

Figure 2. Aboveground (shoot) and belowground (root) biomass (dry mass) in two different forest management systems (high forest and coppice with standards). Data from Bruckman et al. [13].

On average, approximately 40% less biomass is stored in the HF system aboveground, and 7% less belowground (roots). Net primary production (NPP) is higher in CS which compensates lower basal area of the overstorey (DBH > 8 cm) with higher stand density [13]. The main reason of elevated NPP in CS is the higher fertility of chernozems as compared to cambisols in combination with a more effective water holding capacity as compared to the Eutric Cambisol in HF as a consequence of the coarse material content. The underlying silvicultural practices contribute to this biomass pool structure as thinning is performed at regular intervals in HF while typically only one intervention takes place in CS when harvesting coppice and selected standards at the end of the rotational cycle. As a consequence, additional C sequestration may only be achieved in CS when extending the rotation period. The second argument leads to higher productivity of the CS system, which allows higher C sequestration rates.

Bale compression

To reduce long distance hauling cost of forage/hay bales, compression of these bales into ultra-dense bales was adopted by some producers to prepare the hay for overseas transport.

Commercial bale compression equipment has potential to be used for the densification of baled biomass.

Field operation

Number of bales per hour (St. dev.)

Raking

85 (equivalent)

Baling

43 (9)

Accumulating into stacks of bales in field

93 (28)

Loading truck in field from accumulated bales

204 (29)

Loading truck in field from not first accumulated bales

143 (46)

Stacking bales in storage

93 (12)

Table 1. Field capacities of large rectangular baler and bale handlers (Straw M. C., 14% w. b.) [14].

Ten large rectangular switchgrass bales were compressed using the compressor (Figure 4)

[9] . The input bale had a dimension of 0.86×1.22×2.21m, and the resulting compressed bales were 0.53×0.46×0.38m. When stacked in groups of 20 per pallet, the package had a dimension of 1.02×1.17×1.70m. The initial bales had a volume of 23.27m3. When accounting for a 7.0% loss of material and water, this volume was 21.67m3. The bales had average moisture of 14% (w. b.) at the time of compression. The compressed package had a volume of 13.13m3, a reduction of 60.6% in volume.

image46

Figure 4. Commercial large rectangular bale slicer/compressor.

Basic operational parameters of BAC process[18]

To design a BAC system, it is necessary to comprehend the characteristics of water quality, water amount and some certain index of water treatment. First of all, the experiments on the adsorption performance and biodegradability of the waste water are indispensable. Then, according to the result of static adsorption isotherms experiment on the raw water, the appropriate kind of the activated carbon can be chosen, and on the basis of dynamic adsorption isotherms experiment, the basic parameters can be determined. Ultimately, according to the process scale and condition of the field, BAC adsorption devices and its structure as well as supplementary equipment can be determined.

The activated carbon used in BAC process, should be highly developed in the pore structure, especially for the filter pores. Quality of the outflow is directly influenced by the filtering velocity, height of the carbon layer, the retention period and the gas-water ratio. In practice, the general filtering rate is 8-15 km/h. Retention period: According to the different pollutants, the general retention period should be 6-30 min; when the process is mainly removing smelly odor from the raw water, the period should be 8-10 min; when the process is mainly dealing with CODMn, the period should be 12-15 min. Gas-water ratio: As to aerobic microorganism, sufficient DO in the activated carbon layer is needed. Generally, DO>1 mg/L is proper in the outflow, therefore the design is based on a (4-6):1 gas-water ratio, specific details are based on the height of the carbon layer and concentration of organic contaminants. Generally, the thickness of the activated carbon layer is 1.5-3 m, which is determined by the leaping curve of the activated carbon. The growth of microorganisms and suspended solids brought by the inflow on the long-term operating biological carbon bed may block the carbon layer, and the biofilm on the surface of the activated carbon is unlikely to be discovered by naked eyes. Once the thickness is out of limits, the adsorption ability of the activated carbon will be affected undesirably. Therefore, the carbon layer should be washed periodically. Related parameters for backwash are shown in table 1.

Backwash type

Granular activated carbon grade

2.38~0.59 mm

1.68~0.42 mm

Air-water

backwash

Water wash intensity [L/(m2-s)]

11.1

6.7

Water wash interval (min)

8~10

15~20

Air wash intensity [L/(m2-s)j

13.9

13.9

Air wash interval (min)

5

5

Water wash and surface wash

Water wash intensity [L/(m2-s)]

11.1

6.7

Water wash interval (min)

8~10

15~20

Air wash intensity [L/(m2-s)]

1.67

1.67

Air wash interval (min)

5

5

Table 1. Backwash parameters for activated carbon

Hybrid bioreactors

A practically useful solution is compilation of the described above two technologies in one reactor named a hybrid reactor. Both activated sludge and biofilm technologies advantages are utilized in this system.

image106

Figure 2. Microprofiles of biofilm [3]

In this type of reactors (Integrated Fixed Film/Activated Sludge — IFAS, Mixed-Culture Biofilm — MCB, hybrid bioreactors) a secondary settler is used and suspended biomass is returned to the bioreactor, so certain suspended biomass concentration can be maintained. However, when suspended biomass flocs are relatively large (up to 1500 |jm of diameter) they can clog the small pores of carriers [4] resulting in attached biomass growth interruptions and oxygen access limitations.

Additional modifications can reduce energy consumption. The biofilm substratum may consist of various plastic carriers with effective surface area up to several hundred square meters per cubic meter. The volumetric density of carriers with biomass in fluidized beds should be similar to the wastewater density or slightly higher. There are many market — available types of carriers.

Hybrid reactors with moving carriers were firstly developed in Norway in nineties of XXth century. Characteristics of this technology were given firstly by Odegaard et al. [6]. They proposed the carriers filling rate of 70% of volume and obtained the removal efficiency of 91-94% for organic compounds and of 73-85% for nitrogen compounds. The impact of the substrate loading of reactor on the treatment performance was studied by Orantes and Gonzales-Martinez [7] and Andreottola et al. [8]. These researchers applied this technology to the specific conditions — for resorts in Alps. Andreottola et al. [9] and Daude and Stephenson [10] designed such reactor as a small WWTP for 85 p. e.

The hybrid reactor can be designed basing on organic loading of biomass and knowing the geometry of carriers. The number of carriers (N) can be calculated as [11]:

N = (4)

Ak1 ‘ Ab ‘ Gb

where: Ls — removed organic load, kg/d,

Aki — one carrier effective surface area, m2,

Ab* — organic loading of biomass, g/gdmd,

Сь — biofilm surface density, gdm/m2.

The simultaneous application of activated sludge and moving bed technologies has a positive influence on the nitrification process. Paul et al. [12] found that 90% of autotrophs in hybrid bioreactor is a component of biofilm (autotrophs are 40% of total number of microorganisms). Despite relatively low kinetic constants of autotrophs growth and substrate utilisation rate comparing to the heterotrophs (Yh = 0.61 gdm/gcoD, Ya = 0.24 gdm/gcoD, pHmax = 4.55 d-1, pAmax = 0.31 d-1), the high (over 90%) nitrification efficiency in hybrid reactor can be achieved, even in terms of high hydraulic loading rates.

The nitrifying bacteria in the biofilm on the carriers are able to reach the nitrification rate up to 0.8 gN/m2d at 10°C [13] and even up to 1.0 gN/m2d at 15°C [14].

History of BFT

According to [18], BFT was first developed in early 1970s at Ifremer-COP (French Research Institute for Exploitation of the Sea, Oceanic Center of Pacific) with different penaeid species including Penaeus monodon, Fenneropenaeus merguiensis, Litopenaeus vannamei and L. stylirostris [19,20]. Such culture system was compared with an "external rumen", but now applied for shrimp [21]. At the same period, Ralston Purina developed a system based on nitrifying bacteria while keeping shrimp in total darkness. In connection with Aquacop, such system was applied to L. stylirostris and L. vannamei both in Crystal River (USA) and Tahiti, leding considerations on benefits of biofloc for shrimp culture [22]. In 1980, a French scientific program ‘Ecotron’ was initiated by Ifremer to better understand such system. Several studies enabled a comprehensive approach of BFT and explained interrelationships between different compartments such as water and bacteria, as well as shrimp nutritional physiology. Also in 1980s and beginning of 1990s, Israel and USA (Waddell Mariculture Center) started R&D in BFT with tilapia and white shrimp L. vannamei, respectively, in which water limitation, environmental concerns and land costs were the main causative agents that promoted such research (Fig. 1).

image140

Figure 1. Biofloc technology at Ifremer, Tahiti (A), Sopomer farm, Tahiti (B), Waddell Mariculture Center (C) and Israel (D) (Photos A and B: Gerard Cuzon; C: courtesy of Wilson Wasielesky; and D: courtesy of Yoram Avnimelech)

Regarding to commercial application of BFT, in 1988 Sopomer farm in Tahiti (French Polynesia) using 1000m2 concrete tanks and limited water exchange achieved a world record in production (20-25 ton/ha/year with two crops) [22, 23]. On the other hand, Belize Aquaculture farm or "BAL" (located at Belize, Central America), probably the most famous case of BFT commercial application in the world, produced around 11-26 ton/ha/cycle using

1.6 ha lined grow-out ponds. Much of know-how of running worldwide commercial scale BFT shrimp ponds is derived from BAL experience. In small-scale BFT greenhouse-based farms, Marvesta farm (located at Maryland, USA), probably is the well-known successful indoor BFT shrimp farm in USA, can produce around 45 ton of fresh never frozen shrimp per year using ~570 m3 indoor race-ways [24]. Nowadays, BFT have being successfully expanded in large-scale shrimp farming in Asia, Latin and Central America, as well as in small-scale greenhouses in USA, South Korea, Brazil, Italy, China and others (Fig 2). In addition, many research centers and universities are intensifying R&D in BFT, mostly applied to key fields such as grow-out management, nutrition, BFT applied to reproduction, microbial ecology, biotechnology and economics.

image141

Figure 2. Biofloc technology commercial-scale at BAL (A) and Malaysia (B), and pilot-scale in Mexico (C and D) (Photos A, B and D: Mauricio Emerenciano; and C: courtesy of Manuel Valenzuela)

Relevant questions to explore among others include

Can food crop productivity be improved in the context of a sugarcane-based farming system?

Can the understanding of the dimensions of food and livelihood security in sugarcane — based farming systems inform the synergistic development and review of relevant policies in the food, agriculture, health, energy, trade and environment sectors? What are the social impacts of the industry in light of the various agro-ecological zones of the country? What is the gender based livelihood strategies with special emphasis on labor exploitations — child labor etc?

What do people consider as possible options for improving food and livelihood security in a sugarcane-based farming system? Do these options differ between different actors (local women and men, NGOs and government)? How do families cope with food inadequacy, inaccessibility and malnutrition?

Can the study inform the carbon credit market initiative for farming systems in Uganda through the climate smart agriculture concept? Are the proposed assessment tools appropriate for Ugandan situations and the cane-based systems in particular?

5. Conclusion

Driven by the need to meet the increasing local and regional sugar demand, and fossil fuel import substitution, cane expansion has potential negative impact on food security and biodiversity. However, this negative impact parallels the benefits related to cane cultivation. Cane biomass yield can be improved and sustained through the integrated use of various practices reported in this study. Consequently this reduces the need to expand land acreage under cane while releasing land for use in food crop productivity. The high biomass returned to the ground sequesters carbon thereby offering the opportunity for sugarcane based farmers to earn extra income through the sale of carbon credits. Trickle down effects are expected to increase household income through the production and marketing of cane based biofuel and electricity.

These developments are expected to improve the farmers purchasing power, making households to be less dependent on the land and more food secure financially.