This article shows a climate change mitigation strategy by means of membranes replacement and determination methodology of carbon footprint in reverse osmosis (RO) desalination plants, valid for all the islands, and even isolated territories in the continent. This study takes the case of study of Canary Islands, where there are more than 320 desalination plants with different sizes, private, and public. The objective is to propose a new method which integrates this analysis with the replacement of membranes, from 0% to 20% per year in sea water reverse osmosis desalination plants, to reduce the carbon footprint and ecological footprint. If it is considered a replacement of 20% of the elements per year, the carbon footprint could be reduced to between 5% and 6% and even more if it is introduced low energy consumption membranes instead of high rejection elements. The factor mix in Canary Islands, according to the technological structure of the generation park that uses oil products, is around 0.678 kgCO₂/kWh, much higher than in the Spanish mainland where it is 0.263 kgCO₂/kWh. Therefore, it is estimated in Canary Islands 5,326,963 t CO₂/year can be emitted, which represents 2.4 tCO₂/person/year, 12 times more the admissible admissions per inhabitant in the Canary Islands, only considering the seawater desalination sector. This document shows the different results of the analysis of energy efficiency and the environmental footprints. This study may serve as a tool for the decision-making processes related to how to improve energy efficiency in desalination plants.

The penetration of renewable energies in island electricity systems (IESs) poses a series of challenges, which include, among others, grid stability, the response to demand, and the security of the supply. Based on the current characteristics of electricity demand on the islands of the Canary Archipelago (Spain) and their electricity production systems, this study presents a series of alternative scenarios to reduce greenhouse gas (GHG) emissions and increase the penetration of renewable energies. The goal is to optimize combustion-based (nonrenewable) energy production and combine it with renewable-based production that meets the requirements of dynamic response, safety, scaling, and integration with nonrenewable systems in terms of efficiency and power. As verified in the research background, the combination of power producing equipment that is generally employed on the islands is not the best combination to reduce pollution. The aim of this work is to find other possible combinations with better results. A methodology is developed and followed to obtain the lowest GHG production and to determine the measures to be applied based on: (a) changing the fuel type by switching to natural gas in the equipment that allows it; (b) using optimal combinations of the least polluting energy production equipment; (c) integrating, to the extent that it is possible, the Chira-Soria pumped hydroelectric energy storage plant into the Gran Canaria electricity system. A series of alternative scenarios are generated with different operating conditions which show the possibility of increasing the renewable installed capacity in the Canary Islands by up to 36.78% (70% in Gran Canaria), with a 65.13% reduction in GHG emissions and a 71.45% reduction in fuel consumption. The results of this study contribute, through the different measures determined through our research, to the mitigation of GHG emissions.

This paper describes the results that have been obtained in a real case study of a hybrid constructed wetlands system, which has been in continuous operation for over 11 years. The main aim of the study was to understand the long-term operation and efficiency of the system (which is situated in the municipality of Santa Lucía, Gran Canaria, Spain), which comprises two vertical-flow and one horizontal-flow constructed wetlands for the treatment of urban wastewater. The system, which was originally designed to treat a flow rate of 12.5 m³/day, with a load of 100 equivalent inhabitants, has been operating since its inauguration (July 2008), with a flow rate of almost 35 m³/day and a load of 400 equivalent inhabitants. Despite this, the mean total removal efficiencies during the study period (2014–2019) are optimal for a system of these characteristics, as follows: 92% for 5-day biochemical oxygen demand (BOD₅), 89% for the chemical oxygen demand (COD), and 97% for the total suspended solids (TSS). The system efficiency, with respect to nutrient removal, was somewhat lower, resulting in 48% for total N and 35% for NH₄. It has been confirmed with this study that this type of system is an appropriate, robust, resilient nature-based solution for the treatment of the wastewater that is generated in small communities, especially in zones with a warm climate, stable mean temperatures, and mild winters.

This paper reports results of a 5-year trial study of a natural treatment system for wastewater (NTSW) on a livestock pig farm on Gran Canaria (Canary Islands, Spain). The pilot plant consist of a rotary screen, a first-generation multi-chamber digester, and two horizontal subsurface flow treatment wetlands (HSFCW) with a pond installed between them. Results show that the removal efficiency of total chemical oxygen demand (CODt), total suspended solids (TSS), volatile solids (VS) and total dissolved solids (TDS) of the treatment were 91.77%, 95.99%, 82.62%, and 55.78%, respectively. Other removal values include 93.79% for total nitrogen (TN) and 93.05% for phosphorus (P₂O₅). The results demonstrate the suitability of NTSW solutions applied to livestock waste in pig farms and their potential application to other farms of similar size.