title: Sedimentary processes building a tropical delta yesterday, today, and tomorrow: the Mekong System

authors: Nittrouer, Charles A.

abstract: River deltas are important for human habitation, commerce, food, and natural resources. Most terrestrial freshwater, dissolved substances, and suspended sediment supplied to the ocean pass through delta distributary channels. Transitions are complex as this river discharge moves through the serial environments of delta systems: tidal river, estuary, shoreline, continental shelf.

The bulk of Mekong sediment accumulates as a muddy clinoform deposit on the shallow continental shelf (<20–25 m water depth), which forms the foundation over which the subaerial delta surface has grown for the past ~8,000 years. The Song Hau distributary channel, the target of this investigation, receives ~40% of the Mekong discharge and transfers the majority of it to the adjacent shelf during high flow of the river (July–November). Some of the sediment is returned to the channel and to the mangrove shoreline during low flow of the river (December–April). The sediment reentering the channel is mostly mud, deposited by estuarine processes, that temporarily buries the channel bed and interrupts sand transfer to the coastal ocean.

Trapping of sediment supplied to the shoreline of the island, Cu Lao Dung, at the Song Hau mouth, is enhanced by the roughness from dense mangrove roots extending above the bed. Shoreline progradation is asymmetric with the most rapid sediment accumulation (~5 cm yr–1) in the southwestern portion of the island, and the distribution of mangroves is linked to this sedimentation pattern. About one-third of Mekong sediment discharge accumulates in the shelf clinoform near the mouths of the distributary channels, with the greatest accumulation rates (>10 cm yr–1) in the relatively steep foreset region. Intense landward and southwestward currents transport the other two-thirds of Mekong discharge during energetic shelf conditions (December–April). These sediments create a relatively shallow clinoform structure, cause the delta to grow asymmetrically toward the southwest, and form the Ca Mau Peninsula.

In the future, these same natural processes will operate under different conditions. Construction of many dams within the drainage basin (>200 constructed or approved) and the impacts of climate change (i.e., alterations in monsoonal conditions) will significantly decrease Mekong River discharge. In addition, the delta land surface will be flooded due to acceleration of eustatic sea level rise and local land subsidence. Together, loss of river discharge and rise of local sea level will cause many secondary impacts, including erosion of distributary channels, ocean shorelines, and the shelf seabed; saltwater intrusion farther into the channels, along with transfer of associated estuarine processes; and decreased supply of freshwater and solutes, including nutrients, to the coastal ocean. The collaborative research among international and Vietnamese scientists described in this special issue of Oceanography provides an integrated understanding of the Mekong Delta system, and could help formulate strategies to enhance the resiliency of the system and its ability to cope with future impacts.

text: Sedimentary processes building a tropical delta yesterday, today, and tomorrow: the Mekong System River deltas are important for human habitation, commerce, food, and natural resources. Most terrestrial freshwater, dissolved substances, and suspended sediment supplied to the ocean pass through delta distributary channels. Transitions are complex as this river discharge moves through the serial environments of delta systems: tidal river, estuary, shoreline, continental shelf.

The bulk of Mekong sediment accumulates as a muddy clinoform deposit on the shallow continental shelf (<20–25 m water depth), which forms the foundation over which the subaerial delta surface has grown for the past ~8,000 years. The Song Hau distributary channel, the target of this investigation, receives ~40% of the Mekong discharge and transfers the majority of it to the adjacent shelf during high flow of the river (July–November). Some of the sediment is returned to the channel and to the mangrove shoreline during low flow of the river (December–April). The sediment reentering the channel is mostly mud, deposited by estuarine processes, that temporarily buries the channel bed and interrupts sand transfer to the coastal ocean.

Trapping of sediment supplied to the shoreline of the island, Cu Lao Dung, at the Song Hau mouth, is enhanced by the roughness from dense mangrove roots extending above the bed. Shoreline progradation is asymmetric with the most rapid sediment accumulation (~5 cm yr–1) in the southwestern portion of the island, and the distribution of mangroves is linked to this sedimentation pattern. About one-third of Mekong sediment discharge accumulates in the shelf clinoform near the mouths of the distributary channels, with the greatest accumulation rates (>10 cm yr–1) in the relatively steep foreset region. Intense landward and southwestward currents transport the other two-thirds of Mekong discharge during energetic shelf conditions (December–April). These sediments create a relatively shallow clinoform structure, cause the delta to grow asymmetrically toward the southwest, and form the Ca Mau Peninsula.

In the future, these same natural processes will operate under different conditions. Construction of many dams within the drainage basin (>200 constructed or approved) and the impacts of climate change (i.e., alterations in monsoonal conditions) will significantly decrease Mekong River discharge. In addition, the delta land surface will be flooded due to acceleration of eustatic sea level rise and local land subsidence. Together, loss of river discharge and rise of local sea level will cause many secondary impacts, including erosion of distributary channels, ocean shorelines, and the shelf seabed; saltwater intrusion farther into the channels, along with transfer of associated estuarine processes; and decreased supply of freshwater and solutes, including nutrients, to the coastal ocean. The collaborative research among international and Vietnamese scientists described in this special issue of Oceanography provides an integrated understanding of the Mekong Delta system, and could help formulate strategies to enhance the resiliency of the system and its ability to cope with future impacts.

year: 2017

title: Sustainable Energy for New Zealand Dairy Farms by Anaerobic Digestion of Dairy Farm Effluent

authors: Yenamandra, Aparna

abstract: This study evaluated the economic feasibility and environmental impact of using a bio-digester to produce methane for energy production from a New Zealand conventional dairy farm.

Parameters effecting the bio-methanation process are examined. Analytical procedures have been carried out to determine favorable conditions for enhanced biogas production. These were: 1) pH, 2) Temperature, 3) Total solids and Total Volatile solids, 4) Gas volume and 5) Gas analysis.

Using locally supplied dairy shed effluent, it was found that 1 L reactors had peak gas production over 15 days, after which pH dropped and gas production dropped.  Optimal pH was 7 and maximum gas production was 1.25 L/L reactor.

A three stage digester was set up and run for 62 days with a maximum cumulative gas production of 21.3 L, 11.7 L and 6.6 L in the three reactors. Total volumetric methane production was 0.09 m3/kgVS/day 0.06 m3/kgVS/day and 0.07 m3/kgVS/day respectively from reactors 7, 8 and 9. The reactors produced biogas with an average composition of 74 % methane (CH4) and 25% carbon-dioxide (CO2).  A typical digester would produce 65-70% CH4.

1 kg of methane produces 4.66 kWh electricity and 5.72 kWh of heat, a typical farm of 250 cows would produce 548 kWh/day electricity and 665 kWh/day heat from using methane captured in the anaerobic digesters using dairy shed effluent.  A typical 250 cow farm consumes 1285 kWh/day total energy 40% is from heat and rest is electricity. So by having installed plug-flow anaerobic digesters it could potentially meet 130% of total energy needs and 113% of total energy needs by using a three stage mesophilic digester.

A life cycle assessment was carried out for a typical New Zealand farm.  Methane emissions from enteric fermentation, excreta, manure and farm dairy effluent irrigation and storage ponds contribute to 60% of the total greenhouse gas (GHG) emissions of a farm.   Management of dairy shed effluent will only reduce GHG emissions by 1.8%.  In addition, spray irrigation will impact on GHG emissions due increased moisture, C and N content, increasing N2O emissions.  Hence from an environmental sustainability point of view, collecting and digesting diary shed effluent will have little significant impact on overall GHG emissions.  Therefore, collecting and digesting dairy effluent is only of value if it results in economic benefits for the farm.

An economic analysis was conducted on installing a digester system.  The anaerobic digester systems for 250 cow farm would have a capital cost of $107,745 per year, an operating cost of $134,828 per year, and generate revenue of $132,819 per year, but would not be able to pay back the capital cost. For a 250 cow farm a plug flow digester would have a capital cost of $95,658 per year, operating cost $127,018 per year, generate revenue $194,722 per year, and the resulting payback period is 2 years.  A three stage digester for a 250 cow farm would have a capital cost of $259,608 an operating cost of $215,920 per year, generate revenue of $296,389 per year, a payback period of 3 years. But for a large farm size of 600-1000 cows therefore a multi stage digester would be worthwhile. For large dairy farms, CH4 capture with energy recovery can already be cost effective based on the energy value alone.

text: Sustainable Energy for New Zealand Dairy Farms by Anaerobic Digestion of Dairy Farm Effluent This study evaluated the economic feasibility and environmental impact of using a bio-digester to produce methane for energy production from a New Zealand conventional dairy farm.

Parameters effecting the bio-methanation process are examined. Analytical procedures have been carried out to determine favorable conditions for enhanced biogas production. These were: 1) pH, 2) Temperature, 3) Total solids and Total Volatile solids, 4) Gas volume and 5) Gas analysis.

Using locally supplied dairy shed effluent, it was found that 1 L reactors had peak gas production over 15 days, after which pH dropped and gas production dropped.  Optimal pH was 7 and maximum gas production was 1.25 L/L reactor.

A three stage digester was set up and run for 62 days with a maximum cumulative gas production of 21.3 L, 11.7 L and 6.6 L in the three reactors. Total volumetric methane production was 0.09 m3/kgVS/day 0.06 m3/kgVS/day and 0.07 m3/kgVS/day respectively from reactors 7, 8 and 9. The reactors produced biogas with an average composition of 74 % methane (CH4) and 25% carbon-dioxide (CO2).  A typical digester would produce 65-70% CH4.

1 kg of methane produces 4.66 kWh electricity and 5.72 kWh of heat, a typical farm of 250 cows would produce 548 kWh/day electricity and 665 kWh/day heat from using methane captured in the anaerobic digesters using dairy shed effluent.  A typical 250 cow farm consumes 1285 kWh/day total energy 40% is from heat and rest is electricity. So by having installed plug-flow anaerobic digesters it could potentially meet 130% of total energy needs and 113% of total energy needs by using a three stage mesophilic digester.

A life cycle assessment was carried out for a typical New Zealand farm.  Methane emissions from enteric fermentation, excreta, manure and farm dairy effluent irrigation and storage ponds contribute to 60% of the total greenhouse gas (GHG) emissions of a farm.   Management of dairy shed effluent will only reduce GHG emissions by 1.8%.  In addition, spray irrigation will impact on GHG emissions due increased moisture, C and N content, increasing N2O emissions.  Hence from an environmental sustainability point of view, collecting and digesting diary shed effluent will have little significant impact on overall GHG emissions.  Therefore, collecting and digesting dairy effluent is only of value if it results in economic benefits for the farm.

An economic analysis was conducted on installing a digester system.  The anaerobic digester systems for 250 cow farm would have a capital cost of $107,745 per year, an operating cost of $134,828 per year, and generate revenue of $132,819 per year, but would not be able to pay back the capital cost. For a 250 cow farm a plug flow digester would have a capital cost of $95,658 per year, operating cost $127,018 per year, generate revenue $194,722 per year, and the resulting payback period is 2 years.  A three stage digester for a 250 cow farm would have a capital cost of $259,608 an operating cost of $215,920 per year, generate revenue of $296,389 per year, a payback period of 3 years. But for a large farm size of 600-1000 cows therefore a multi stage digester would be worthwhile. For large dairy farms, CH4 capture with energy recovery can already be cost effective based on the energy value alone.

year: 2016

title: Kaupapa Maori research: An indigenous approach to creating knowledge

authors: Bishop, Russell

subjects: Maori

abstract: This paper seeks to identify how issues of epistemological racism are addressed in practice
within an indigenous Kaupapa (philosophy) Maori approach to research, and how such
considerations may impact on the Western trained and positioned researcher. One fundamental
understanding to a Kaupapa Maori approach to research is that it is the discursive practice
that is Kaupapa Maori that positions researchers in such a way as to operationalise selfdetermination
(agentic positioning and behaviour) for research participants. This is because the
cultural aspirations, understandings and practices of Maori people implement and organise the
research process. Further, the research issues of power; initiation, benefits, representation,
legitimation, and accountability are addressed and understood in practice by practitioners of
Kaupapa Maori research through the development of a participatory mode of consciousness.

text: Kaupapa Maori research: An indigenous approach to creating knowledge This paper seeks to identify how issues of epistemological racism are addressed in practice
within an indigenous Kaupapa (philosophy) Maori approach to research, and how such
considerations may impact on the Western trained and positioned researcher. One fundamental
understanding to a Kaupapa Maori approach to research is that it is the discursive practice
that is Kaupapa Maori that positions researchers in such a way as to operationalise selfdetermination
(agentic positioning and behaviour) for research participants. This is because the
cultural aspirations, understandings and practices of Maori people implement and organise the
research process. Further, the research issues of power; initiation, benefits, representation,
legitimation, and accountability are addressed and understood in practice by practitioners of
Kaupapa Maori research through the development of a participatory mode of consciousness.

year: 1999